La Metallurgia Italiana, n.11/12 Novembre-dicembre 2021

La

Metallurgia Italiana

International Journal of the Italian Association for Metallurgy

n. 11/12 novembre/dicembre 2021 Organo ufficiale dell’Associazione Italiana di Metallurgia.

Rivista fondata nel 1909

La Metallurgia Italiana International Journal of the Italian Association for Metallurgy Organo ufficiale dell’Associazione Italiana di Metallurgia.

House organ of AIM Italian Association for Metallurgy.

Rivista fondata nel 1909

Direttore responsabile/Chief editor: Mario Cusolito Direttore vicario/Deputy director: Gianangelo Camona Comitato scientifico/Editorial panel: Livio Battezzati, Christian Bernhard, Massimiliano Bestetti, Wolfgang Bleck, Franco Bonollo, Bruno Buchmayr, Enrique Mariano Castrodeza, Emanuela Cerri, Lorella Ceschini, Mario Conserva, Vladislav Deev, Augusto Di Gianfrancesco, Bernd Kleimt, Carlo Mapelli, Jean Denis Mithieux, Marco Ormellese, Massimo Pellizzari, Giorgio Poli, Pedro Dolabella Portella, Barbara Previtali, Evgeny S. Prusov, Emilio Ramous, Roberto Roberti, Dieter Senk, Du Sichen, Karl-Hermann Tacke, Stefano Trasatti Segreteria di redazione/Editorial secretary: Marta Verderi Comitato di redazione/Editorial committee: Federica Bassani, Gianangelo Camona, Mario Cusolito, Carlo Mapelli, Federico Mazzolari, Marta Verderi Direzione e redazione/Editorial and executive office: AIM - Via F. Turati 8 - 20121 Milano tel. 02 76 02 11 32 - fax 02 76 02 05 51 met@aimnet.it - www.aimnet.it Immagine in copertina: Shutterstock

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La

Metallurgia Italiana

International Journal of the Italian Association for Metallurgy

n. 11/12 novembre/dicembre 2021 Organo ufficiale dell’Associazione Italiana di Metallurgia.

Rivista fondata nel 1909

Editoriale / Editorial Editoriale

A cura di F.Bonollo, G. Timelli............................................................................................................ pag.04

Memorie scientifiche / Scientific papers Pressocolata / Die Casting

Study of the effect of ultrasonic treatment in porosity and mechanical properties of cast parts M. da Silva, S. Cruz, X. Planta, J. Tort, G. Aguirre......................................................................................... pag.06

Comparison between high-pressure die-cast and rheo-cast aluminium-SiCp MMC; Wear and friction behaviour

n.11-12 novembre/dicembre 2021 Anno 113 - ISSN 0026-0843

E.W. Jarfors, C.K. Jammula, R. Ghasemi ............................................................................................ pag.13

Effect of Li addition on mechanical properties of Al-Si-Mg alloy

O. Özaydin, A.Y. Kaya, E. Armakan .................................................................................................. pag.19

Numerical simulation of the effects of a Phase

Z. Noohi, B. Niroumand, G. Timelli................................................................................................... pag.25

Characterization of microstructural and mechanical properties of high-pressure die-cast EN AC 46000 alloy

M. Tocci, L. Montesano, A. Pola, S. Ferri.......................................................................................................... pag.31

Alternative alloying concepts of hot work tool steels for application in die casting

indice

P. Niederhofer, F. van Soest, M. Gürcan, H.-G. Krull, T. Schneiders.................................................... pag.37

CS1 - The new hot-work tool steel for die casting dies with the highest surface requirements

E. Meurisse, I. Schruff ......................................................................................................................... pag.43

AM process simulation to optimise diecasting tooling

N. Gramegna, D. Boscolo, G. Scarpa, N. Nardo, F. Bonollo................................................................. pag.49

Residual stress analysis applied to HPDC aluminium components: a case study

E. Fracchia, F.S. Gobber, M. Rosso, Y. Kobayashi, C. Mus................................................................... pag.54

Evaluation of fracture toughness in HPDC aluminum alloys to estimate crashworthiness in Automotive parts

I. Tarhouni, D. Frómeta, A. Lara, S. Parareda, I. Tarhouni, D. Casellas................................................. pag.60

Temperature and microstructural-condition dependence for thermal diffusivity and electrical conductivity of a casting Al-Si-Cu-Mg alloy

R. Wang, M.C. Poletti, B. Stauder, R. Fernández Gutiérrez, C. Confalonieri, E. Gariboldi....................... pag.67

Effects of bismuth on the characteristics of eutectic Si particles in Na-modified A356 alloys

Ö. Gürsoy, G. Timelli........................................................................................................................... pag.73

Fatigue properties and microstructural analysis of diecast AlSi11Cu2(Fe) alloy: effect of surface finishing

M. Merlin, D. Benasciutti, L. Lattanzi, A. Fortini, G. Timelli.................................................................. pag.79

Attualità industriale / Industry news

Micro spray technologies for an efficient die spraying in HPDC

edited by: M. Lutz................................................................................................................................ pag.85

Atti e notizie / AIM news

Eventi AIM / AIM events......................................................................................... pag.90 RAIDMAP 2021 relazione finale............................................................................ pag.91 Metallurgia 2040......................................................................................................... pag.93 Comitati tecnici / Study groups ........................................................................... pag.98 Normativa / Standards......................................................................................... pag.102 Indice analitico /Analytic index.......................................................................... pag.106 Indice autori / Author index................................................................................ pag.110

“

editoriale - editorial

“Il prossimo Convegno Na-

zionale AIM metterà in risalto la centralità della metallurgia

“The next National AIM

Congress will highlight the

central role of Metallurgy

rispetto alle sfide ambientali

with respect to the envi-

affrontando”.

challenges that we are

e industriali che il mondo sta

F. Bonollo, G. Timelli

Prof. Franco Bonollo Università degli studi di Padova

ronmental and industrial Prof. Giulio Timelli Università di Padova - DTG, Vicenza

facing”

F. Bonollo, G. Timelli

I CONVEGNI AIM E IL FUTURO DELLA METALLURGIA

AIM CONGRESSES AND THE FUTURE OF METALLURGY

La Metallurgia è una disciplina viva e in continua evoluzio-

Metallurgy is a dynamic and continuously evolving scien-

ne, che è stata essenziale nello sviluppo industriale e che

ce, which has been essential for industrial development

sarà sempre più strategica in un’ottica di transizione ener-

and which will play a strategic role in the context of energy

getica, sostenibilità ed economia circolare.

transition, sustainability and circular economy.

È stato questo aspetto ad emergere con maggior rilievo

This has been one of the key-output from High Tech Die

dal Convegno Internazionale High Tech Die Casting 2021

Casting 2021 Conference (a selection of papers is publi-

(di cui in questo numero si pubblica una selezione di me-

shed in this issue). High Pressure Die Casting industry and,

morie). L’industria della pressocolata e, più un generale,

more generally, the Aluminium industry have shown its

dell’alluminio ha dimostrato la sua capacità di rinnovarsi,

innovation capability, facing new challenges (high quality

accettando nuove sfide (getti ad elevata qualità, leghe ri-

castings, high-performance recycled alloys, new applica-

ciclate ad elevate performance, nuove applicazioni per la

tions addressed to e-mobility, innovative approaches for

mobilità elettrica, innovativi approcci di monitoraggio e

monitoring and controlling processes) and developing

controllo dei processi) e proponendo soluzioni basate

solutions based on metallurgical knowledge and strongly

sulla conoscenza metallurgica e fortemente interconnesse

related to digitalization, energy management, lightweight

con aspetti legati alla digitalizzazione, alla gestione ener-

design.

getica, al lightweight design.

This interdisciplinary approach will be the peculiarity of Questo approccio interdisciplinare sarà l’elemento distin-

the next National AIM Congress (Padova, september 21st-

tivo anche del prossimo Convegno Nazionale AIM (Padova,

23rd, 2022), which will highlight the central role of Me-

21-23 settembre 2022), che metterà in risalto la centralità

tallurgy with respect to the environmental and industrial

editoriale - editorial

della metallurgia rispetto alle sfide ambientali e industriali

challenges that we are facing. The Congress will show the

che il mondo sta affrontando. Il Convegno illustrerà l’enor-

enormous potential associated to the cooperation betwe-

me potenziale che è insito nelle collaborazioni tra Univer-

en University and Industry (including both large Compa-

sità e mondo dell’industria (dalla grande impresa alle realtà

nies and SMEs with high innovation attitude), and will put

medio-piccole a forte vocazione innovativa), evidenziando

into evidence, also in the metallurgy field, how a networ-

come, anche nel settore metallurgico, sia sempre più de-

ked way of working (International Networks, Technologi-

cisivo operare in una logica di reti di collaborazioni diffuse

cal Clusters, Regional Innovative Networks) and knowle-

(Network Internazionali, Cluster Tecnologici e Reti Innova-

dge integration approach will be more and more crucial.

tive Regionali) e con uno spirito di piena integrazione delle conoscenze.

The document “Metallurgia 2040”, published in this issue and elaborated by the Board of COMET (the AIM Commit-

Questo approccio è ulteriormente testimoniato dal docu-

tee collecting all Italian Metallurgy professors and resear-

mento “Metallurgia 2040”, pubblicato in questo numero ed

chers) is a further example of this approach. The document

elaborato dalla Giunta di COMET, il Comitato AIM che rac-

some considerations about the way of teaching Metallur-

coglie tutti i docenti universitari di Metallurgia. Il documen-

gy, which must develop and transfer concepts such as in-

to offre alcuni spunti di riflessione per quello che riguarda

ter-disciplinarity and transversality, taking advantage from

la didattica metallurgica, che dovrà sempre più sviluppare i

all the cooperation between Metallurgy professors and

concetti di trasversalità e inter-disciplinarietà, valorizzando

Industry. A continuous University-Industry integration has

le numerose collaborazioni di ricerca tra i docenti di Metal-

been always promoted and achieved by AIM, and is a qua-

lurgia e l’industria. Una continua integrazione tra Università

lifying point for science and engineering education paths.

e Industria è, da sempre, promossa e realizzata dall’AIM, ed

In the future, the central role of Metallurgy will be confir-

è un elemento qualificante nei percorsi formativi in ambito

med by the development of professional skills (young gra-

ingegneristico e scientifico. La centralità della metallurgia

duates but also professionals involved in lifelong learning)

troverà sempre più affermazione grazie allo sviluppo di

working as “experts of the metallurgy domain”.

profili professionali (neo-laureati, ma anche professionisti

The “metallurgist of the future” must be fully involved in

inseriti in un contesto di formazione permanente) in grado

the general scenarios of ecological and digital transtions,

di agire da “esperti del dominio metallurgico”.

and, thanks to his/her knowledge about phenomena asso-

Il “metallurgista del futuro” deve essere pienamente con-

ciated to metallic alloys, is able of understanding and ela-

sapevole degli scenari generali delle transizioni ecologica

borating high amounts of data and information, and thus

e digitale e, grazie a solide conoscenze dei fenomeni e dei

of individuating, suggesting and validating sustainable and

processi che coinvolgono le leghe metalliche, è in grado

reliable technological solutions.

di interpretare ed elaborare moli crescenti di informazioni e di individuare, proporre, validare soluzioni tecnologiche sostenibili e affidabili.

Memorie scientifiche - Pressocolata

Study of the effect of ultrasounic treatment in porosity and mechanical properties of cast parts M. da Silva, S. Cruz, X. Planta, J. Tort, G. Aguirre

Ultrasonic treatment has gained interest as aluminium melt degassing treatment lately due to its environment friendly feature. This paper describes the effect of ultrasonic degassing in preparing melt for different aluminium alloys for permanent mould casting and high pressure die casting. Efficiency of ultrasonic degassing is compared with conventional

lance degassing, by direct measurements of hydrogen concentration in the melt with a Hycal probe and by reducedpressure test in different stages of the casting process. Significant reduction in dross formation along was shown for

ultrasonic degassing as compared with conventional lance degassing. The mechanical properties, microstructure and porosity level of components produced by high pressure die casting and permanent mould casting after both

degassing techniques are determined. It is observed that the degassing efficiency of one and other degassing method depends on the treated aluminium alloy. The results show that the components produced after ultrasonic degassing

treatment have similar hardness, tensile properties, porosity level and microstructure as the components degassed with conventional lance degassing. However, ultrasonic treatment seems to have an effect on porosity distribution, reducing the amount of big pores and distributing the porosity more homogenously.

KEYWORDS: AULTRASONIC DEGASSING, HYDROGEN CONTENT, HIGH PRESSURE DIE CASTING, PERMANENT MOULD CASTING INTRODUCTION

Ultrasonic degassing of liquid metals has long history. As early as in the 1940s Esmarch et al. studied the degassing

of Al–Mg alloys by sonic vibrations induced by contactless electromagnetic stirring and vibrations in the crucible [1].

Starting from the 1960s laboratory and pilot-scale trials of ultrasonic degassing for foundry and later wrought alloys

have been performed and summarized by G.I. Eskin [2].

Indeed, already early investigations conducted by Altman et al. [3] demonstrated that the removal of hydrogen

from aluminium alloys depends greatly on the acoustic power transferred to the melt and on the development of cavitation.

The efficiency of ultrasonic degassing is a function of

input ultrasonic power, melt temperature, melt flow, and

Manel da Silva, Sylvia Cruz

Eurecat, Centre Tecnològic de Catalunya, Spain.

Xavier Planta Ultrasion, S.L., Spain.

Jaume Tort, Gonzalo Aguirre Hornos y Metales, S.A., Spain.

alloy composition. The fundamental studies on these issues have been published elsewhere [2, 4].

Despite successful industrial trials in the 1960–1970s,

ultrasonic degassing was not adopted as a mainstream technology due to arrival of Ar-assisted degassing. In

La Metallurgia Italiana - Novembre/Dicembre 2021

pagina 6

Scientific papers - Die casting

recent years, however, the intrinsic features of ultrasonic

degassing stipulated comeback interest to this technology that may answer the current environmental challenges.

In addition, new level of ultrasonic technology makes its application easier.

alloy and 725±20ºC for AlSi7Mg alloy during the degassing

treatment. The experiments were conducted using a prototype specifically designed to treat large volumes

of molten aluminium. An image of the prototype is shown in Fig. 1. The ultrasonic equipment used in the

This paper reports the results of pilot-scale trials of

ultrasonic degassing using a prototype specifically

designed for the application, applied to two of major

foundry technologies, i.e. high-pressure die casting and permanent mould casting.

experiments was composed of: a 5-kW USGC-5-22 MS ultrasonic generator, a 5-kW MST-5-18 water-cooled

magnetostrictive transducer, a titanium booster, all

supplied by Reltec (Russia), and a niobium tip (Fig. 1).

During the treatment the sonotrode was moved with the prototype over the surface of the melt. Between 4 and 4.5

EXPERIMENTAL PROCEDURE

Ultrasonic degassing treatments were conducted for

20 min for AlSi7Mg and 10 min for AlSi9Cu3(Fe). The treatment was conducted in a crucible holding furnace with a capacity of 400 kg filled up with about 300kg. The

kW of power in the range of 17-18 kHz were applied in the molten metal. Alternatively, a 20 min degassing treatment with a porous graphite lance bubbling N2 was introduced

in the same amount of metal, with the same temperature and composition.

temperature of the alloy was 690±20ºC for AlSi9Cu3(Fe)

Fig.1 - Experimental set-up used in the experiments, general view of the prototype (left) and detail of the ultrasonic generator and wave-guiding equipment (right).

Measurements of the hydrogen with a Reduced Pressure

Test (RPT) (MK, Germany) were made before and after the degassing treatment, 15 minutes and 1 hour after the treatment. Additionally, the hydrogen content was directly measured with an Hycal probe. After the degassing treatment, the melt was used to cast components using a

High Pressure Die Casting (HPDC) unit (Bühler Evolution 53D), AlSi9Cu3(Fe) alloy, and a mould for Permanent Mould Casting (PMC), AlSi7Mg alloy.

La Metallurgia Italiana - November/December 2021

One

randomly

selected

part

produced

after

each

degassing treatment by PMC was inspected by computed tomography. Additionally, parts produced by PMC and HPDC were sectioned in order to control their tensile

properties and microstructure. In Fig. 2 are presented pictures of the parts, indicating the regions where the

specimens were extracted. The tensile properties were determined according to ISO 6892-1 standard.

pagina 7

Memorie scientifiche - Pressocolata

Fig.2 - Images of a PMC part (left) and HPDC part (right) indicating the regions where the specimens for tensile test and metallographic inspection were extracted.

RESULTS AND DISCUSSION

to record the actual hydrogen present in the melt during

In Table 1 are presented the Density Index measured in the

different tests is presented in Fig. 3. After the treatment,

Permanent Mould Casting of AlSi7Mg alloy

ultrasonic degassing treatment and the reference lance degassing. In both treatments the Hycal probe was used

the whole trial. The hydrogen evolution observed in the

21 parts were produced for each batch, with a stair shaped permanent mould by gravity casting.

Tab.1 -D.I index values measured for the lance degassing and ultrasonic treatment of AlSi7Mg alloy.

Sample number

20 min lance degassing

20 min ultrasonic treat.

Before treatment (1)

5.65

8.69

After treatment (2)

0.37

1.40

15 min after treatment (3)

0.47

4.10

1 hour after treatment (4)

2.48

6.98

Ambient temperature

22.7ºC

13.1ºC

Relative humidity

32 %

92 %

Dross weight

2075 g

239 g

It is observed that both treatments are quite effective,

considerably reducing the initial Density Index value.

After this first drop in the Density index, it increases again,

but without reaching the initial value. Lance degassing seems to be more effective than ultrasonic degassing,

but the reduction with ultrasonic treatment is also very

significant. In addition, can be observed that ambient humidity was much higher in the day where ultrasonic

La Metallurgia Italiana - Novembre/Dicembre 2021

treatment was conducted, leading to a faster regassing of the metal, once the degassing treatment concluded [4].

Regarding the dross formed during the treatment, lance

degassing generates almost 10 times the dross that is

created with ultrasonic treatment, increasing the dross rate from 0.08 % to 0.69 %. The highly turbulent conditions

created by gas degassing generate a disturbance in the aluminium surface that enhance dross formation. On

pagina 8

Scientific papers - Die casting

the contrary, ultrasonic processing, creates very small

heating system, is transferred into a similar oscillation on

break the oxide layer covering the melt surface [5].

is hidden by the temperature variation.

cavities that are turned into bubbles that practically do not

hydrogen value, and the effect of the degassing treatment

Regarding the results of Hycal measurements (Fig. 3), it can be observed that the hydrogen content has a clear relation

with the furnace temperature. The natural oscillation of temperature experienced by the melt, due to furnace

Fig.3 - Hydrogen evolution measured with Hycal equipment for the utrasonic (left) and lance (right). Blue curve belongs to measured hydrogen concentration and orange to measured melt temperature.

5 PMC parts of AlSi7Mg were selected from each batch for

pore distribution in the ultrasonic degassed parts. The

from each of the parts and tested in a universal testing

regarding effect on ductility and other mechanical

subsequent inspection. A tensile specimen was machined machine. The results are summarized in Table 2.

As can be seen in Table 2, the results obtained with the

ultrasonic degassed parts are slightly better than the

nitrogen degassed parts. Nevertheless, the difference is in the level of the sum of both standard deviations, not allowing to infer any strong conclusion.

pores below this size of 0.1 mm3 are much less relevant properties than the biggest ones, as the equivalent size in one single dimension for this volume is 33 μm, a value

just over the 29 μm obtained in the SDAS measurement of

current material for both degassing routes. Pores below SDAS size do not to have a relevant impact on mechanical properties, as do larger pores [7].

One part produced from the nitrogen degassed batch (N2) and one part produced from the ultrasonic degassed

batch (US) were selected for detailed measurement of their porosity distribution with computed tomography.

The results with the percentage of pores found for each pore size interval are presented in Fig. 4. The results

show that the number of larger pores (with a volume over

0.1 mm3) is clearly higher in the N2 degassed part. This

behavior has been observed previously [6], but it is still not

clear the mechanism to lead to this more homogeneous

La Metallurgia Italiana - November/December 2021

pagina 9

Memorie scientifiche - Pressocolata Tab.2 - Section measured for the tensile specimens and values obtained from the corresponding tensile test.

Part

Ultrasonic

degassed

Rp0.2

Rm

At (corr.)

Part

%

number

Rp0.2

MPa

Rm

MPa

At (corr.)

N2-2

118

172

2.16

N2-5

104

170

3.17

N2-6

111

169

2.78

N2-12

112

151

1.69

number

MPa

MPa

US-2

117

157

2.28

US-3

115

171

3.26

US-6

121

174

2.23

US-8

117

174

2.78

US-10

117

177

3.02

N2-13

99

155

2.51

Average

117

171

2.71

Average

109

163

2.46

Desvest

2

8

0.45

Desvest

7

10

0.57

Nitrogen

degassed

%

HIGH PRESSURE DIE CASTING OF ALSI9CU3(FE)

Reduced Pressure Test samples were taken from the metal

Two treatments were used alternatively in the melt 10

(2), after 15 minutes of idle time (3) and 1 hour after the

ALLOY

min ultrasonic degassing and 20 min lance degassing

treatment. After the treatment the metal was used to produced HPDC components with a HPDC machine.

before the treatment (1), immediately after the treatment

treatment (4). In Table 3 are presented the results of Density Index obtained for this alloy with both degassing treatments.

Fig.4 - Total pore size distribution in percentage of total number of pores for the ultrasonic degassed and lance degassed parts (left) and only considering the pores with a size over 0.05 mm3 (right).

Tab.3 - D.I index values measured for the lance degassing and ultrasonic treatment of AlSi9Cu3(Fe) alloy.

Sample number

20 min lance degassing

10 min ultrasonic treat.

Before treatment (1)

5.14

4.17

After treatment (2)

4.99

0.09

15 min after treatment (3)

3.08

4.50

1 hour after treatment (4)

2.43

4.74

Ambient temperature

14.5ºC

16.1ºC

Relative humidity

59 %

75 %

Dross weight

555 g

240 g

La Metallurgia Italiana - Novembre/Dicembre 2021

pagina 10

Scientific papers - Die casting

The lance degassing reduces the density index slightly after the treatment, and degassing continues after

production has started. In the ultrasonic treatment a strange value of just 0.09 is obtained immediately after the ultrasonic treatment, but after that the other two remaining samples (3 and 4) shows similar D.I. values

than the initial melt. With the obtained results, it seems that the effect of the 10 min ultrasonic treatment in the D.I. is insignificant. Nevertheless, it is observed that both treatments are not very effective with this AlSi9Cu3(Fe)

alloy, having a very limited impact on the D.I. value.

Regarding the dross formed during the treatment, lance

degassing generates more than double of the dross that is created with ultrasonic treatment, increasing the dross rate from 0.08 % to 0.19 %.

As well, as for AlSi7Mg alloy, 5 HPDC components were selected from each production in order to characterize

their mechanical properties. The values obtained in the tests for each lot of parts are summarized in Table 4.

No significant differences in the obtained mechanical properties

are

observed

between

both

degassing

methods. All the samples present similar values of yield strength, ultimate tensile strength and elongation.

Tab.4 - Section measured for the tensile specimens and values obtained from the corresponding tensile test.

number

Part

MPa

MPa

Rm

At (corr.) %

number

MPa

MPa

Rm

At (corr.)

181

120

243

0.5

161

121

249

0.5

186

113

230

1.3

163

114

229

0.7

190

129

267

0.5

164

125

260

0.9

191

126

257

0.9

169

118

235

0.9

193

108

216

0.8

171

114

225

0.8

Average

US

119

243

0.8

Average

N2

118

240

0.8

Desvest

US

9

20

0.4

Desvest

N2

5

15

0.2

Ultrasonic

degassed

Rp0.2

Part

Nitrogen

degassed

Rp0.2

%

CONCLUSIONS

ACKNOWLEDGEMENTS

following conclusions can be inferred:

support provided by EuroStars program granted by Eureka

From the results obtained in the present study the - Ultrasonic degassing performed using a single

ultrasonic source and a prototype-level setup is able to achieve similar hydrogen content in the melt than a mature, commercially available porous lance for an

The authors would like to acknowledge the financial

and funded, in Spain, by CDTI under Grant Agreement CIIP-20172025. The authors gratefully acknowledge all help provided by the members of the consortium.

appreciable melt volume of 300 kg of AlSi7Mg alloy.

- The melt surface is much less disturbed during

ultrasonic degassing, as cavitation bubbles are formed within the metal and the flow is directed downwards.

As a result, much less dross formation is observed as compared to lance degassing.

- Porosity and mechanical properties of the castings

produced after ultrasonic degassing or lance degassing

are similar with some tendency of reduction of large pores content after ultrasonic degassing.

La Metallurgia Italiana - November/December 2021

pagina 11

Memorie scientifiche - Pressocolata

REFERENCES [1] [2] [3] [4] [5] [6] [7]

W. Esmarch, T. Rommel, K. Benther. Werkstoff-Sonderheft. W.V. Siemens Werke, Berlin;1940; 78–87 p.

G.I. Eskin, D.G. Eskin. Ultrasonic Treatment of Light Alloy Melts, 2nd ed. CRC Press, Boca Raton; 2014.

M.B. Altman, D.V. Vinogradora, V.I. Slotin and G.I Eskin. On the effects of ultrasound on molten metals, Izv. Akad. Nauk SSSR, Otd. Tekhn. Nauk. 1958; 9: 25-30.

D. Eskin, N. Alba-Baena, T. Pabel, M. da Silva. Ultrasonic degassing of aluminium alloys: basic studies and practical implementation.

Mater Sci Technol. 2015; 31:79-84.

M. da Silva, L. Rebolledo, T. Pabel, T. Petkov, X. Planta, J. Tort, D. Eskin. Evaluation of effect of ultrasonic degassing on components produced by low pressure die casting. Internat J Cast Metals Research. 2015; 28: 193-200.

M. da Silva, A. Bajusz, T. Pabel, T. Petkov, X. Planta. Evaluation of the effect of ultrasonic degassing on components produced by high pressure die casting. The 73rd World Foundry Congress. Krakow: Poland; 2018. 341-342.

A. Niklas, S. Orden, A. Bakedano, M. da Silva, E. Nogués. A.I. Fernández-Calvo. Effect of solution heat treatment on gas porosity and mechanical properties in die cast step part manufactured with a new AlSi10MnMg(Fe) secondary alloy. Mat Sci & Eng A. 2016; 667: 376-382

La Metallurgia Italiana - Novembre/Dicembre 2021

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Scientific papers - Die casting

Comparison between high-pressure die-cast and rheo-cast aluminium-SICp MMC; wear and friction behaviour A. E. W. Jarfors, R. Ghasemi, S. Awe, C. K. Jammula

Aluminium is essential in automobile industry together with cast iron. Because of its lightweight property and good mechanical properties, aluminium reinforced with silicon carbide have found application as brake discs. Aluminium reinforced with 15% and 20% silicon carbide were high-pressure die-cast (HPDC) and Rheo-HPDC cast in the current paper. Micro-Vickers hardness and Rockwell C hardness showed different trends with the increasing amounts of SiCp-particles. Scratch resistance of the surface on micro-scale was analysed using a micro-scratch test to study the mechanics of the wear process.

Reciprocating sliding wear of the composites was considered, using the HPDC cast aluminium with 20% silicon carbide of liquid casting as the sliding surface. The wear showed a combination of abrasive wear and adhesive wear. The metallography of the wear surfaces showed deep abrasive wear grooves. Wear debris from both the surfaces were forming a tribolayer. The formation of this layer decided the friction and wear performance as a result of the abrasive and adhesive wear mechanisms seen both in the micromechanics of the scratch test and in the friction behaviour.

KEYWORDS: ALUMINIUM, METAL MATRIX COMPOSITE, HIGH-PRESSURE DIE-CASTING, RHEOCASTING, WEAR

BACKGROUND The need for lightweight solution for moving parts in transport solutions increases as requirements on energy efficiency and carbon footprint are increasing. Weight reduction is vital for carbon footprint reduction. (1) Brake disc rotors is an example of a critical component targeted for weight reduction. (2). Aluminium MMC brake rotors are fabricated using stir casting. (3) Al-SiCp MMCs commonly used requires that Si is present as an alloying element to stabilize the SiCp particles. (2) As a consequence, the Al-SiCp has a matrix that is nearly eutectic, even though other examples exists. (3). In the current study, the friction and wear performance was investigated for two levels of SiCp additions (15 and 20%) fabricated by stir casting and subsequently cast. The casting process studied were conventional high-pressure die-casting and

Anders E. W. Jarfors

Jönköping University, School of Engineering, Department of Materials and Manufacturing, Box 1026, 55111 Jönköping, Sweden

Rohollah Ghasemi

Husqvarna AB, Drottninggatan 2, 561 82 Huskvarna, Sweden

Samuel Awe

Automotive Components Floby AB, Aspenäsgatan 2, 521 51 Floby, Sweden

Chaitanya Krishna Jammula

Jönköping University, School of Engineering, Department of Materials and Manufacturing, Box 1026, 55111 Jönköping, Sweden

rheocasting. The aim was here to better understand the wear and friction performance by modifying the matrix and particle distributions.

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Tab.1 - Composition of the materials investigated.

Materials

Si

Fe

Mg

Ti

Al

SiCp

L15

2.94

1.09

0.51

0.04

81.36

15

L20

1.82

1.23

0.57

0.025

76.17

20

S15

2.38

1.11

0.54

0.04

81.31

15

S20

1.94

1.32

0.58

0.023

76.07

20

EXPERIMENTAL

Nano vantage test machine with a depth sensor. Three mi-

Materials and Casting

cro-scratches were made under progressive load, increa-

The Al-MMC material was cast using conventional high

sing from 5 mN to 1000 mN with a length of 1000µm. The

pressure die casting and through rheocasting. In rheo-

scratch test was made according to ISO 14577- 1:2002, at

process was used to prepare

25°C. A sphero-conical shaped diamond tip with a cone

casting, the RheoMetal

TM

the slurry, with the so-called enthalpy exchange material

angle 2θ=90o was used. (4)

made from the same material as in the melt. In the rheoca-

Dry Sliding Wear Test: Reciprocating sliding wear test

sting process, the same high pressure die casting set-up

using a pin on plate test under dry conditions, suitable

was used to cast the slurry. Spectrometer and EDS analy-

for brake discs, especially for holding brakes was made.

sis are used to get information about the chemical com-

(5) The pin samples were flat-ended with 8mm diameter

position of the material. The chemical composition of the

and 20mm length. Pins are made from all materials. The

material is shown in table 1. It should here be noted that

substrate was made from the L20 material (50mm length,

the resulting composition of the L15 and S15 material is

20mm width and 15mm thick). The test load was 20N me-

that the matrix has a slightly higher Si-content as compa-

asured using a load cell. Both normal force and friction

red to the L20 and L20 samples that are richer in SiC.

force was measured to evaluate the coefficient of friction (CoF). For each material, five pins were tested up

Microstructural analysis

to 120mins. The pin wear was measured base on weight

An Olympus GX microscope was to study the micro-

change with an accuracy of 0.0001 g. Each sample was cle-

structure. For the quantitative analysis t. Quantitative par-

aned ultrasonically in acetone and dried before measure-

ticle characteristics analysis was made using the Olympus

ment. All tests were carried out at room temperature. The

stream image analysis software. To better reveal the mi-

worn surfaces of the pins were examined under Scanning

crostructure; the composite material was etched using a

Electron Microscope, (SEM).

10% NaOH and distilled water solution.

RESULTS AND DISCUSSION Hardness and wear testing

Microstructure

Hardness Test: Hardness was measured using the Rockwell

The microstructure is shown in Fig. 1. The particle num-

C and Micro-Vickers hardness test. The Rockwell C test

ber density is clearly higher for the 20% SiC additions as

was carried out at room temperature, with a 50 kgf load

compared to the 15% additions. It is also visible that for

with a dwell time of 10-15 seconds at six different loca-

the semisolid cast samples, coarser light α-Al regions are

tions per sample. Rockwell hardness was converted into

visible (S15 and S20), not visible in the conventionally cast

Brinell harness for comparison taking into considera-

samples (L15 and L20).

tion the maximum value of 800 BHN. The Micro-Vickers hardness test was carried out at room temperature with 100gms load with a dwell time of 10-15 seconds.

Micro-Scratch Test: Micro-scratch test was carried out on

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Scientific papers - Die casting

Fig.1 - Illustration of the microstructures with L15 and L20 samples being cast using conventional high-pressure die casting and S15 and S20 being cast using rheocasting. Scale bar is 100µm.

The nearest neighbour distances vary primarily between

ces, Fig. 2b shows that the distribution differences betwe-

the 15 and 20% SiC additions and there are no significant

en S20 and L20 are nearly none, and only the L15 and S15

differences in the average distance between the S15 and

samples show differences. L15 shows a more even distri-

L15 and the S20 and L20, Fig. 2a). This suggests that the

bution compared to L20 and S20. Comparing S15 to L15,

differences should be due to the additional level (15 or

S15 has a broader distribution, especially with a higher

20 % SiC) and not between the casting methods (S or L

contribution from large nearest neighbour distances. S15

samples). The distribution of nearest neighbour distan-

also har a higher fraction in the range below 10µm.

Fig.2 - Nearest neighbour distances a) averages and error, b) distribution of nearest neighbour distances.

HARDNESS TEST

as such is affected by deformation hardening taking pla-

The Micro-Vickers hardness did not show any significant

ce during the indentation. The matrix properties may thus

differences between the different samples, Fig. 3a. The

become dominant. The variation suggests that the matrix

20%SiC addition resulted in a larger scatter of the data.

of the semisolid cast materials is softer than the conven-

Rockwell C hardness displayed substantial differences in

tionally cast material. It should particularly be noted that

hardness, decoupled from the SiC particle addition, Fig.

L15 is much harder than S15. Converting the Rockwell

3b. L15 was the hardest, followed by L20 and S20 whilst

C data to Brinell hardness showed the same trend, even

S15 was the softest, Fig. 3b. The difference between the

though the Brinell scale was capped at 800, Fig. 3c.

Micro-Vickers test and the Rockwell C test is that Micro-Vickers is based on intent size and thus depending on the plastic deformation. Rockwell C is based on the difference in displacement depths between two loads and

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Fig.3 - Hardness of the composite, a) Micro-Vickers results, b) Rockwell C hardness results, c) Brinell hardness converted from Rockwell hardness.

MICRO SCRATCH TEST

samples, a breakthrough threshold above 200mN for S15

In the scratch test, there is a clear difference between the

and above 400mN for S20 indicating a possible instability

semisolid materials and the conventionally cast mate-

due to limited subsurface strength.

rials, Fig. 4. The scratch hardness was an inversely proportional load for the L15 and L20. For the semisolid cast

Fig.4 - Scratch test using progressive load.

DRY SLIDING WEAR TEST Based on the Archard equation (6), the slope under constant load should be linear Eq (1)

Where v is average sliding speed (m/s), t is the duration

wear loss was S20>L20>L15>S15. A higher SiC addition,

(s), F is load (kgf), H is hardness (Brinell hardness) and K

(L20 and S20) resulted in a higher wear rate than the lower

is a material system parameter that depends on the wear

additions (L15 and S15). Furthermore, the hardest mate-

and contact mechanisms (adhesive or abrasive wear). Eq

rial L15 showed a higher mass loss than the softest ma-

(1) implies that increased hardness gives the lower wear

terial S15. This implies that the material hardness is not

rate. Based on the results, Fig. 3c, the material weight

dominant but rather the nature of the contact between

loss should be S15>S20>L20>L15. In Fig. 5, the rate of

the surfaces, implicitly included in the coefficient K. (6)

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Scientific papers - Die casting

Fig.5 - a) Mass loss from the dry sliding wear test b) CoF during the sliding wear test.

Friction also depends on contact characteristics and me-

S20 supported by an increased presence of silicon in EDS

asured through the CoF, Fig. 4 b), but an increase in fri-

analysis compared to S15. The Si originated from exposed

ction cannot explain the difference in wear performance

SiCp-particles in the surface. L20 showed open pores in

between S15 and S20. Noteworthy is that the hardest ma-

the trbolayer with clusters of SiCp-particles visible. L20

terial, L15, had the lowest CoF and the material with the

showed less debris compared to S20 which suggests that

lowest wear rate, S15, was the softest, with the highest

the tribolayer was more stable in L20. Abrasive wear was

CoF. The time-series data of the CoF, Fig. 6, shows cle-

more predominant in L20 compared to L15 and S15, sup-

ar differences between the different materials. Firstly, the

porting that the tribolayer was necessary for the wear resi-

average CoF value corresponds to the floor value of CoF

stance of Al-SiCp-MMC. The importance of the tribo-layer

under steady-state conditions. Besides, several adhesi-

build-up is also visible in the CoF shown in Fig. 6. The fri-

ve wear events generate a CoF above unity. S20 displays

ction coefficient first starts on low but varying values indi-

the highest number of adhesive events. L15 and S15 show

cating adhesive episodes. Later this is stabilising close to

lower amounts of adhesive events, compared to L20 and

the average values with more adhesive events.

S20. Adhesive wear performance is thus important for Al-SiCp composites. The worn surfaces showed significant differences, Fig. 7. Both S15 and L15 showed adhesive wear as material smearing with burr formation in L15.

This suggests a more abrasive nature of wear in L15, compared to S15. Smearing with loose debris was found in S20 surface. This indicated that tribo-layer was unstable in

Fig.6 - CoF as a function over time for samples L15, L20, S15 and S20 illustrating the number of adhesive events where the friction force exceeds the normal force.

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Fig.7 - Wear surface samples L15, L20, S15 and S20 illustrating the adhesive and abrasive nature of the wear mechanisms as well as the stability of the tribo-layer. (Scale bar is 100µm).

CONCLUSIONS

ture of the contact has a great influence on the wear, re-

In the current study, the wear performance of conventio-

sulting in that the softest material with the highest friction

nally cast Al-SiCp MMCs was studied. It was shown that

coefficient had the lowest wear.

there is a highly complex interaction between the wear and friction properties of the material. The wear loss as

ACKNOWLEDGEMENTS

function could not be established clearly as suggested by

The materials supplied by AC Floby, but cast at Jönköping

hardness as suggested by Archard’s law. Instead, the na-

University as part of an MSc project.

REFERENCES [1]

[2] [3] [4] [5] [6]

Serrenho AC, Norman JB, Allwood JM. The impact of reducing car weight on global emissions: the future fleet in Great Britain. Philos Trans R Soc A Math Phys Eng Sci [Internet]. 2017;375(2095):20160364. Available from: http://rsta.royalsocietypublishing.org/lookup/ doi/10.1098/rsta.2016.0364 Sadagopan P, Natarajan HK, Praveen Kumar J. Study of silicon carbide-reinforced aluminum matrix composite brake rotor for motorcycle application. Int J Adv Manuf Technol. 2018;94(1–4):1461–75.

Sijo MT, Jayadevan KR. Analysis of Stir Cast Aluminium Silicon Carbide Metal Matrix Composite: A Comprehensive Review. Procedia Technol [Internet]. 2016;24:379–85. Available from: http://dx.doi.org/10.1016/j.protcy.2016.05.052 Ghasemi R, Johansson J, Ståhl JE, Jarfors AEW. Load effect on scratch micro-mechanisms of solution strengthened Compacted Graphite Irons. Tribol Int [Internet]. 2019;133(January):182–92. Available from: https://doi.org/10.1016/j.triboint.2019.01.010 Poulios K, Drago N, Klit P, De Chiffre L. A reciprocating pin-on-plate test-rig for studying friction materials for holding brakes. Wear.

2014;311(1–2):40–6.

Popov V. Generalized archard law of wear based on rabinowicz criterion of wear particle formation. Facta Univ Ser Mech Eng. 2019;17(1):39–45.

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Scientific papers - Die casting

Effect of Li additions and holding time on the mechanical properties of the AlSiM9mg alloys O. Özaydın, Y. Kaya, D. Dışpınar

Aluminum alloys are widely used in industry due to their lightness and ease of machining. Concurrently, the mechanical properties of aluminum alloys can be increased by different development studies. Grain refining, modification and heat treatment can be given as examples of these development studies. In this study, the influences that may occur in mechanical properties by adding lithium (Li) additions, which are generally used for lightening in aviation applications, to AlSi9Mg alloy at different levels have been investigated. Due to the slag problems especially at high Li ratios, a study with relatively low Li addition ratios has been developed. At the same time, the effect of Li additions on high temperature and holding times was also studied. According to the results of the study, it was observed that a high amount of slag was formed at the high Li addition level and the mechanical properties were in a decreasing trend. In addition, it has been observed that the increase in Li level negatively affects the fluidity. It was also observed that the holding times dramatically decreased the Li values in the aluminum alloy structure, this decrease occurred in the ultimate tensile strength (UTS) and yield strength (YS), while the unit elongation (%) increased slightly.

KEYWORDS: ALSI9MG, ALUMINUM ALLOYS, HOLDING TIME, ALLI5 ADDITIONS, MECHANICAL PROPERTIES INTRODUCTION The usage of aluminum and its alloys have increased in many applications and industries in last years. Although aluminum alloys are used in the aviation, marine and defense industries, the automotive industry is the largest market for castings [1]. Aluminum is increasingly used and demanded in the automotive industry due to the increasing fuel efficiency demand and emission regulations in last decades. In addition to its low density, it shines among other alternatives with its excellent castability, high specific strength and easy processability. Thanks to these properties, aluminum alloys are preferred in many automotive parts such as wheels, cylinder heads, engine blocks, brackets and pistons [2].

Onur Özaydın

Department of Research and Development, Cevher Wheels, Izmir, Turkey (E-mail address: oozaydin@cevherwheels.com)

Yiğit Kaya

Department of Research and Development, Cevher Wheels, Izmir, Turkey

Derya Dışpınar

Chemical and Metallurgical Engineering Faculty, Istanbul Technical University, Istanbul, Turkey

Lei et al. studied on the influences of Li on the microstructure and properties of hypoeutectic Al-7Si alloy.

They used various techniques to characterize the microstructural evolution. Tensile tests were performed to investigate the mechanical properties of the alloys with varying Li additions. In conclusion, the effects of varying La Metallurgia Italiana - November/December 2021

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Memorie scientifiche - Pressocolata Li additions of the Al-7Si alloy are that the addition of Li

ductility [6].

remarkably changed the morphology of eutectic Si and the coarse AlLiSi intermetallic phase was observed in the

Karamouz et al. investigated on the effects of lithium (Li)

alloys with increasing Li content greater than 0.2%. With

on the microstructure, hardness and mechanical proper-

the 0.1% Li addition, the as-cast alloy obtained the best

ties of casted A380 aluminum alloy. In the results, Si pha-

tensile properties compared to the other experimental al-

ses changed from course structure into the fine structure

loys [3].

with increase of Li content up to 0.1%. Tensile tests that with addition of 0.6% Li, the ultimate tensile strength

Ashtari et al. investigated on the influence of Li addition

(UTS) and elongation values increased from 274 to 300

on the intermetallic compounds in Al–6.5%Si–3.5%Cu–

MPa and 3.8% to 6%, respectively. Adding 0.03–0.1% Li to

1%Fe cast alloys. According to their study, Li successfully

the A380 aluminum alloy decreased the hardness values

modifies the morphology of the β-Al5FeSi phase from co-

of the alloys. In presence of 0.03–0.1% Li UTS and elonga-

arse intersected and branched platelets into finer and in-

tion of the A380 aluminum alloy were improved. Among

dependent ones. They noted at the end of their study that

the Li-containing A380 aluminum alloys, specimens with

the addition of Li should be carefully controlled to add

addition of 0.06% Li exhibit the best mechanical proper-

minimum amount to avoid the AlLiSi phase formation [4].

ties [7].

Karamouz et al. studied on the influence of heat treat-

Mørtsell et al. have study about the effects and beha-

ment and lithium content on microstructure and mecha-

viour of Li and Cu alloys in Al-Mg-Si alloys. They noted

nical properties of A380 aluminum alloy. In their study,

that smaller amounts of Cu and Li also improves thermal

the effects of a T4 heat treatment on the microstructure

stability. By substituting some Mg with Li, it is possible to

and tensile properties of an A380 aluminum alloy with and

achieve higher strength to weight ratios without altering

without lithium (Li) additions have been investigated. The

the precipitation sequence of the alloys or sacrificing the

results showed that when the T4 heat treatment was ap-

hardening potentials [8].

plied, spheroidized eutectic Si particles and β-phase particles were formed. Significant improvements in tensile

Koshino et al. characterized the microstructure the Al-

properties were also observed in heat-treated samples. In

Mg-Si(-Li) alloys by transmission electron microscopy

conclusion, they noted that T4 heat treatment improves

(TEM), energy dispersive X-ray spectroscopy (EDS) and

the tensile properties for both non-modified and modi-

atom probe tomography (APT) [9].

fied alloys. T4 heat treatment and the addition of Li to A380 aluminum alloy have considerable influences on the mi-

MATERIALS AND METHODS

crostructure [5].

As mentioned before, the main automotive manufacturers are demanding aluminum alloy wheel product due to low

Din et al. added different range of Li to conventional Al-

density, high specific strength, high corrosion resistance,

0.9Mg-0.5Si alloy in their work. The levels are 0, 1, 2 and

good machinability, and recyclability. AlSi7 and AlSi11 are

3 wt.% Li respectively. The extruded samples are aged to

the most used materials in wheel production [10]. Never-

investigate the effect of Li addition on the metallurgical

theless, the alternative materials as AlSi9 are investigated

and mechanical properties. In the results, the density of

in this study. Base metal melting was carried out at 720 °C

conventional alloy was reduced up to 7.8% while the ul-

using 10 kg SiC (graphite) crucibles. Li master alloying was

timate tensile strength (UTS) increased by 62% with 3%

carried out at 720 ± 30 °C. The application temperature was

Li addition. Microstructure results showed that, Li was ef-

determined from the phase diagram specific to AlLi5 ma-

fective in reducing the grain size. The ageing trend first

ster alloy. While determining the range; “Multicomponent

decreased for 1 wt.% Li addition and then increased with

Phase Diagrams: Applications for Commercial Aluminum

increasing Li content from 2 to 3 wt.% at the expense of

Alloys – Alloys with Lithium” [11] and “Microstructure

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Scientific papers - Die casting characterization of as-cast Al–Mg–Si alloys with high con-

metal in these two stages and its effect on the metallur-

tent Li element addition” [12] were used.

gical-mechanical properties were investigated. When the

The trial casting with various Li master alloy was started.

chemical analysis results were evaluated, no abnormal si-

In the trial castings, 0.1 and 0.2 wt% were chosen in the

tuation was observed in the trial castings (Table 1-4). The

castings. Additionally, one hour of holding period at the

1-hour waiting period resulted in noticeable reductions

melting temperature was investigated in order to see the

in Li levels. This result also supported the knowledge of

change of elements such as Li, which has the risk of bur-

Li master alloy to burn (decompose) after holding at high

ning at high temperature. The change in the content of the

temperature.

Tab.1 - Chemical composition of the AlSi9 with Li (%0.1) and Holding Time t=0 h.

SI [%]

FE [%]

CU [%]

MN [%]

MG [%]

ZN [%]

TI [%]

CR [%]

8,593

<0,050

0,0030

<0,0010

0,141

<0,0010

0,116

<0,005

NI [%]

PB [%]

SN [%]

NA [%]

CA [%]

ZR [%]

V [%]

BE [%]

0,0027

<0,0020

<0,0010

0,000

0,0030

0,0013

0,012

0,000

LI [%]

CO [%]

SB [%]

P [%]

B [%]

AL [%]

0,086

0,0011

0,014

<0,001

<0,000

90,94

Tab.2 - Chemical composition of the AlSi9 with Li (%0.1) and Holding Time t=1 h.

SI [%]

FE [%]

CU [%]

MN [%]

MG [%]

ZN [%]

TI [%]

CR [%]

8,629

<0,046

0,0036

<0,0010

0,144

<0,0010

0,115

<0,005

NI [%]

PB [%]

SN [%]

NA [%]

CA [%]

ZR [%]

V [%]

BE [%]

0,027

<0,0020

<0,0010

0,000

0,0024

0,0015

0,012

0,0000

LI [%]

CO [%]

SB [%]

P [%]

B [%]

AL [%]

0,025

0,0006

0,0059

<0,0010

<0,000

90,98

Tab.3 - Chemical composition of the AlSi9 with Li (%0.2) and Holding Time t=0 h.

SI [%]

FE [%]

CU [%]

MN [%]

MG [%]

ZN [%]

TI [%]

CR [%]

8,583

0,051

0,0023

<0,0010

0,140

<0,0010

0,113

<0,0050

NI [%]

PB [%]

SN [%]

NA [%]

CA [%]

ZR [%]

V [%]

BE [%]

0,0027

<0,0020

<0,0010

0,000

0,0032

0,0013

0,012

0,000

LI [%]

CO [%]

SB [%]

P [%]

B [%]

AL [%]

0,230

0,0014

0,0092

<0,0010

<0,000

90,81

Tab.4 - Chemical composition of the AlSi9 with Li (%0.2) and Holding Time t=1 h.

SI [%]

FE [%]

CU [%]

MN [%]

MG [%]

ZN [%]

TI [%]

CR [%]

8,455

<0,044

0,0019

<0,0010

0,135

<0,0010

0,116

<0,005

NI [%]

PB [%]

SN [%]

NA [%]

CA [%]

ZR [%]

V [%]

BE [%]

0,026

<0,0020

<0,0010

0,000

0,0024

0,0015

0,012

0,000

LI [%]

CO [%]

SB [%]

P [%]

B [%]

AL [%]

0,029

0,0012

<0,0010

<0,0010

<0,000

90,90

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Fig.1 - Macrostructures.

Tab.5 - Microstructures.

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Scientific papers - Die casting

Tab.6 - Mechanical properties of First Trial Casting.

CONCLUSIONS

ACKNOWLEDGE

It was concluded that Li addition could not reach the de-

The authors would also like to acknowledge financial sup-

sired improvement in the elongation values in AlSi9 alloy,

port by The Scientific and Technological Research Coun-

the fluidity was negatively affected by the increasing Li le-

cil of Turkey (TUBITAK Project Number: 3181044) and

vel, and as the holding time was increased, the Li ratio was

Cevher Wheels Co. where done experimental sections

decreased approximately 70%.

performed in this study.

REFERENCES [1] [2] [3] [4] [5]

[6]

[7]

Dispinar, D.: “Determination of Metal Quality of Aluminium and Its Alloys (PhD Thesis)” (pp.1-4). School of Metallurgy and Materials – The University of Birmingham. January 2005.

Davis J R (editor), ASM Specialty Handbook: Aluminum and Aluminum Alloys, 1993, ASM International.

Lei, W., Liu, X., Wang, W., Sun, Q., Xu, Y., Cui, J.: “On the influences of Li on the microstructure and properties of hypoeutectic Al-7Si alloy” (pp.703-706) Journal of Alloys and Compounds. 30 December 2017. DOI: 10.1016/j.jallcom.2017.04.295 Ashtari, P., Tezuka, H., Sato, T.: “Influence of Li addition on intermetallic compound morphologies in Al-Si-Cu-Fe cast alloys” (pp.4346) Scripta Materialia. 17 April 2004. DOI: 10.1016/j.scriptamat.2004.03.022 Karamouz, M., Azarbarmas, M., Emamy, M.: “On the conjoint influence of heat treatment and lithium content on microstructure and mechanical properties of A380 aluminum alloy” (pp.377-382) Materials and Design. 20 February 2014. DOI: 10.1016/j. matdes.2014.02.033 Din, ud S., Kamran, J., Tariq, N.H., Hasan, B.A., Petrov, R.H., Bliznuk, V., Zuha, uz S.: “The synergistic effect of Li addition on microstructure, texture and mechanical properties of extruded Al-Mg-Si alloys” (pp.11-22) Materials Chemistry and Physics. 28 February 2016. DOI: 10.1016/j.matchemphys.2016.02.029 Karamouz, M., Azarbarmas, M., Emamy, M., Alipour, M.: “Microstructure, hardness and tensile properties of A380 Aluminum alloy with and without Li additions” (pp.409-414) Materials and Engineering A. 29 June 2013. DOI: 10.1016/j.msea.2013.05.088

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[8]

[9]

[10] [11] [12]

Mørtsell, A.E., Marioara, C.D., Andersen, S.J., Ringdalen, I.G., Friis, J., Wenner, S., Røyset, J.; Reiso, O., Holmestad, R.: “The effects and behaviour of Li and Cu alloying agents in lean Al-Mg-Si alloys” (pp.235-242) Journal of Alloys and Compunds. 23 December 2016.

DOI: 10.1016/j.jallcom.2016.12.273 Koshino, Y., Kozuka, M., Hirosawa, S., Aruga, Y.: “Comparative and complementary characterization of precipitate microstructures in Al–Mg–Si(–Li) alloys by transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography” (pp.765-770) Journal of Alloys and Compunds. 7 November 2014. DOI: 10.1016/j.jallcom.2014.10.199 Ozaydin, O., Armakan, E., Kaya, A. Dokumacı, E., (2019) The Effects of Artificial Ageing Conditions on A356 Aluminum Cast Alloys.

ECHT 2019 European Conference on Heat Treatment, Bardolino / Italy.

Nikolay A. Belov Dmitry G. Eskin Andrey A. Aksenov. (2005) Multicomponent Phase Diagrams: Applications for Commercial Aluminum Alloys (pp.257-286) Elsevier Science eBook ISBN: 9780080456966 DOI:10.1016/B978-0-08-044537-3.X5000-8 Xiaokun Yang, Baiqing Xiong, Xiwu Li, Lizhen Yan, Zhihui Li, YongAn Zhang, Hongwei Liu, Hongwei Yan and Kai Wen (2019) Mater.

Res. Express 6 IOP Publishing Ltd https://doi.org/10.1088/2053-1591/ab4f06

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Scientific papers - Die casting

Numerical simulation of the effects of a Phase Change Material (PCM) on solidification path of gravity sand cast Al-Cu alloy Z. Noohi, B. Niroumand, G. Timelli

Solidification structure has a significant effect on mechanical and physical properties of metallic materials and its control is a main direction in the research for the improvement of materials performance. Various methods, such as control of cooling rate, inoculation, imposing vibration and pressure, are traditionally used to control the solidification structure during casting and solidification processes. In this paper, the preliminary results of a new method for controlling the solidification structure during casting using Phase Change Materials (PCMs) are presented. The evolution of the solidification structure of a directionally chilled Al-Cu alloy poured in a silica sand mould with and without the use of pure zinc as a PCM was examined using experimental and simulation methods. It was shown that the PCM temperature could reach about 510 °C during the solidification of the aluminium alloy, therefore, absorbing its melting latent heat from the solidifying aluminium alloy melt which affects its local solidification cooling rate. Therefore, the solidification structure of the sample cast in the PCM fitted mould differed from that of the sample without PCM. While macrostructures of both samples showed the transition from columnar to equiaxed grains, the columnar zone in the PCM sample was larger than in the sample without PCM. In other words, columnar to equiaxed transition (CET) for the sample without PCM occurred sooner than that for the sample with PCM. In addition, the average size of the equiaxed grains at the Chill sample is smaller than the PCM sample.

KEYWORDS: MACROSTRUCTURE CONTROL, GRAVITY SAND CASTING, PHASE CHANGE MATERIALS (PCMS), COLUMNAR TO EQUIAXED TRANSITION (CET) INTRODUCTION

Aluminium casting alloys have huge applications in automotive, sport, and aerospace industries because of such

special properties as excellent thermal and electrical conductivity, appropriate castability, reasonable weldability, lightweight and good corrosion resistance [1, 2]. It has been

established that different processing parameters including cooling rate [3], application of electric and magnetic fields [4] and directional solidification [5] can affect the casting macro and microstructure as well as the solidification path.

Using metal or graphite chillers is another way to control the final casting structure as well as to produce castings

with minimum shrinkage defects. Different types of chil-

ler materials such as copper, iron, or aluminium based al-

Zohrehsadat Noohi

Department of Materials Engineering, Isfahan University of Technology, 84156-83111, Isfahan, Iran

Behzad Niroumand

Department of Materials Engineering, Isfahan University of Technology, 84156-83111, Isfahan, Iran

Giulio Timelli

Department of Management and Engineering, University of Padova, 36100, Vicenza, Italy

loys as well as graphite can be used according to their heat

capacities and diffusivities. It is obvious that each of these materials can absorb and transfer a specific amount of heat before saturation by heat. Therefore, both type and dimen-

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Memorie scientifiche - Pressocolata

sions of chillers have an important role on heat transfer, co-

melting of the PCM (pure Zn) during solidification of the Al-

[6]. Obviously, larger chillers are required for higher heat ab-

of the castings, alumina insulation (not shown in the figure)

oling rate, and solidification microstructure of the castings sorption, and the areas closer to the chill experience higher

cooling rates resulting in the formation of fine columnar microstructures [7].

In this paper, a new way to control the solidification macrostructure of metallic alloys by using Phase Change Materials

(PCMs) is proposed. PCMs are materials that can absorb or release their latent heat at a relatively constant temperature

(their melting temperature) during the solid-liquid transition

Cu alloy and to further encourage directional solidification was used around the casting cavity.

The Al-Cu alloy was melted and superheated to 750 °C in a graphite crucible using a resistance furnace and cast in two

moulds fitted either with a chill (Chill sample) or with PCM (PCM sample), as shown in Fig. 1. In the Chill sample, a so-

lid chiller with 30×30×13 mm3 dimensions was placed at the end of the casting. In the PCM sample, a steel container with

30×30×25 mm3 dimensions and wall thickness of 2 mm fil-

[8]. PCMs are mainly used in such applications as buildings

led with pure zinc was used. In order to evaluate the effects

dy, a PCM has been incorporated into a metal chiller and its

and solidification structure of the Al-Cu alloy, dimensions of

a directionally solidified Al-Cu alloy is investigated using

they had the same cooling power as that of the solid chiller

[9] and solar systems [10] to save heating energy. In this stu-

of the latent heat absorption of the PCM on the cooling rate

effect on the cooling and solidification macrostructure of

the PCM and the encasing box were selected in a way that

experimental and simulation methods.

up until the melting of the PCM.

EXPERIMENTAL PROCEDURE

lidification of the alloy, three K-type thermocouples were

Al-4.5wt.%Cu-0.2wt.%Fe alloy, low carbon steel and com-

surface. One thermocouple in the chiller (in the Chill sam-

chiller and PCM, respectively. Schematics of the casting

were also employed (Fig. 2). The temperature data was col-

sodium silicate bonded silica sand. The casting dimensions

of 1 s-1, analog-to-digital converter accuracy of 0.1°C, which

For recording the temperature during the pouring and so-

ALLOY AND CASTING METHOD

located in the castings at 10, 35 and 60 mm from the chill

mercially pure zinc were considered as the poured metal,

ple) and two thermocouples in the PCM (in the PCM sample)

moulds are illustrated in Fig. 1. The moulds were made of

lected using a data acquisition system with a sampling rate

were 30×30×70 mm3. In order to provide enough time for

was linked to a personal computer.

Fig.1 - Schematics of the casting moulds: (a) Chill sample and (b) PCM sample.

MACROSTRUCTURE INVESTIGATION

CASTING SIMULATION

gitudinal sections of the cast samples were ground by sili-

based on numerical simulation with ProCast 2018 softwa-

In order to study the macrostructure of the castings, loncon carbide (SiC) papers to 600 grit and etched with Keller

etchant (1.5 ml HCl, 2.5 ml HNO3, 1 ml HF and 95 ml distilled

water).

La Metallurgia Italiana - Novembre/Dicembre 2021

Before casting, the optimum mould designs were obtained re. Tetrahedral mesh number was chosen 209517 for the casting, 17078 for the chiller, 43510 for the steel container, 71214 for the PCM, 124499 for the runner system, 285639 for

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Scientific papers - Die casting

the insulator and 431920 for the mould. The heat transfer coefficients were selected according to Tab. 1. The mass flow was selected at 200 g/s.

Tab.1 - Heat transfer coefficients (HTC) between different interfaces of the moulds.

Cast-Chill

Cast-Insulator

Cast&RunnerMould

PCM-Chill

InsulatorMould

Chill-Mould

Chill sample

4500-5500

200

900

---

50

600

PCM sample

8000-10000

200

1000

9000-15000

50

800-1000

RESULTS AND DISCUSSION

is shown in Fig. 2. It shows that the PCM temperature at po-

Fig. 2 demonstrates the collected experimental temperatu-

419.5 °C, after 11 s and finally reaches about 510 °C after 40

EXPERIMENTAL RESULTS

re-time (T-t) curves of both Chill and PCM samples at different positions. According to Fig. 2, for the Chill sample,

all the thermocouples in the casting rapidly reached 750 °C

and then were cooled gradually. The chiller temperature also reached 600 °C. On the other hand, for the PCM sample, the temperature reaches about 600 °C at 10 and 35 mm

from the chill surface before dropping down suddenly and

rising again to 600 °C in less than 100 s. Then they continue a gradual cooling process. At 60 mm from the chill surface, the temperature reaches 750 °C, then cools down to about

650 °C where it remains almost constant for about 150 s and

then starts to decrease. The differences among the curves at the early stages of the casting are thought to be related to

the turbulence of the melt during metal pouring when the molten metal may touch the thermocouples temporarily.

Furthermore, the T-t curves of two positions inside the PCM (a)

sition Zn1 reaches the melting point of the pure zinc, i.e.

s. The PCM temperature at position Zn2 reaches its melting

point after 30 s and finally increases to about 500 °C after 120 s. The latent heat absorption effect of the PCM is evident in the curve corresponding to Zn2. According to Fig. 2, at the early stages, the PCM sample has cooled faster than the Chill sample because of the effect of PCM melting.

The thermophysical properties of zinc are different from

steel. The specific heat coefficient of pure zinc, at both solid and liquid phases, is less and its heat conductivity is more than steel [11, 12]. Therefore, the heat transfer in the PCM

sample would be more than that in the Chill sample, resulting in a faster temperature drop in the PCM sample. Moreover, when the pure zinc starts to melt at the early stages,

it absorbs its latent heat from the Al alloy. This extra heat absorption is believed to affect the cooling rate and, consequently, the macrostructure of the aluminium alloy casting. (b)

Fig.2 - (a) Experimental T-t curves for both PCM and Chill samples and (b) Location of three thermocouples at 10, 35, and 60 mm from the chiller surface in both PCM and Chill samples, one thermocouple in the chiller (Chill sample) and two thermocouples, i.e. Zn1 and Zn2, in the PCM (PCM sample).

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Fig. 3 illustrates the macrostructures of both samples. Each macrostructure consists of a columnar structure grown on

the chill surface followed by an equiaxed grain structure

towards the ingate of the casting. A clear CET (Columnar-Equiaxed Transition) is observed in both castings. Length of

columnar regions, measured using ImageJ analysis software, is equal to about 38 and 41 mm for Chill and PCM samples, respectively.

According to Fig. 3(a), a distinct difference between the two

macrostructures is that solidification in the chill sample ap-

pears to has started from the lower corner of the steel chill

and the columnar grains have grown towards the upper surface of the Chill sample. On the other hand, all the columnar

grains grew uniformly perpendicular to the chill surface in

the PCM sample with a direction opposite to that of the heat

transfer. The difference is believed to be related to the air gap between the PCM and the steel container. In the Chill

sample, when the molten metal first touches the lower part of the solid steel chiller during pouring, an intense heat tran-

sfer sets in, resulting in rapid nucleation and growth of grains from the contact area. The total chilling capacity of the solid

chiller is concentrated on this small contact area. Due to the large volume of the chiller, it is not easily saturated by the

transferred heat. As a result, the grains grow in the opposite direction to the heat transfer. Therefore, these localized nu-

tact points.

The air gap is practically removed when the encapsulated

PCM melts. Melting of the PCM, on the one hand, increases the heat transfer between the casting and the chiller/PCM

assembly and, on the other hand, absorbs its latent heat

from the casting. As a result, the cooling rate of the PCM sample increases and its solidification time decreases resulting in a larger columnar zone compared to those of the Chill

sample, as shown in Fig. 4. The average size of the equiaxed grains was calculated by the lognormal distribution method

[13]. According to related equations, the average grain sizes

are 1.8 ± 1.3 mm and 2.2 ± 1.8mm for the Chill and PCM samples, respectively.

Previous researches have shown that by determining the

thermal gradient (G) at the solid-liquid interface and the solid-liquid interface velocity (R), it is possible to predict the

CET formation [14-16]. It has been shown that CET will occur

when the G/R ratio decreases and reaches below a critical

value. Upon decreasing the thermal gradient in front of the

solid-liquid interface, the constitutional undercooling in

front of the solidification front increases and equiaxed grains can grow in an unconstrained manner [15]. In this work, the measured amount of G/R (according to the simulated T-t curves) at the time of CET formation was about 14.9 and 0.05 °C·s/cm2 for the Chill and the PCM samples, respectively.

cleation and heat transfer phenomena at the lowest corner

Higher G/R value in the Chill sample means that CET took

sample.

tion growth. In other words, the formation of CET at the Chill

2 mm thick steel container. When the molten metal comes

the Chill sample, the equiaxed zone has occurred at a closer

participate in the heat transfer at the beginning due to the

crostructure.

of the chiller have determined the grain orientation of this

place at a higher thermal gradient and/or smaller solidifica-

In the PCM sample, however, the PCM is encapsulated in a

sample is easier than that in the PCM sample. Therefore, in

in contact with the steel chiller, the PCM cannot effectively

distance to the chiller surface, and as a result, has a finer ma-

presence of an air gap between the PCM (pure Zn) and the steel chiller. Therefore, the steel container wall heats up quickly avoiding a localized heat transfer from the first con(a)

(b)

Fig.3 - Macrostructure of (a) Chill and (b) PCM samples.

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Scientific papers - Die casting

SIMULATION RESULTS

At a distance of 10 mm from the chiller, the cooling rate at

Figs. 4(a) and 4(b) show the experimental and simulation T-t

the mushy zone near the solidus temperature is about 4.6

diagrams of the Chill and PCM samples, respectively. As it

and 7.7 °C/s for the Chill and the PCM specimens, respecti-

is observed, there is a good agreement between the simu-

vely. At greater distances (x=35 and x=60 mm), the cooling

lation and the experimental data. The cooling rate near the

rates in the PCM sample are even larger than those in the

liquidus temperature was measured at different points ac-

Chill sample. These differences are thought to be due to the

cording to the simulation diagrams in the temperature range

presence of the PCM (pure zinc), i.e. because of different

of 644-634 °C. The cooling rate at the chiller/casting interfa-

physical properties in comparison to solid steel chiller and

ce (x=0 mm) for both samples is about 28.6 °C/s suggesting

its melting at the early stages of casting solidification. As a

how the dimensions of the chiller and PCM were correctly

result, the chilling powers in both samples were similar be-

designed, i.e. they provide a similar chilling effect at the be-

fore melting the PCM, but the cooling rate and solidification

ginning.

conditions changed after melting the PCM.

(a)

(b)

Fig.4 - Experimental and numerical cooling curves for (a) Chill and (b) PCM samples.

CONCLUSION

can be used as an innovative cooling system to control the

In this paper, a novel method to control the solidification

solidification macrostructure of the castings.

macrostructure of an Al-Cu alloy using Phase Change Materials (PCMs) was studied using experimental and simula-

ACKNOWLEDGMENTS

tion approaches. The results showed that the incorporation

ZN would like to thank Isfahan University of Technology

of a zinc PCM into a metal chiller affected the cooling and

(IUT), Iran, and the Ministry of Science, Research and Tech-

solidification conditions of a directionally solidified Al-Cu

nology of Iran for the financial supports, and the University

alloy. Columnar to Equiaxed Transition (CET) was observed

of Padova (Italy) for providing some of the required pieces

in both samples. However, it occurred later for the sample

of equipment.

fitted with the zinc PCM. The effects are believed to be due to absorption of the latent heat of melting of the PCM during the early stages of solidification of the casting as well as the different thermophysical properties of the PCM and chill materials. Based on the results, the proposed method

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REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]

Qi M, Li J, Kang Y. Correlation between segregation behavior and wall thickness in a rheological high pressure die-casting AC46000 aluminum alloy. J. Mater. Res. Technol. 2019; 8: 3565-3579.

Babaee M.H, Niroumand B, Maleki A, Lashani Zand M. Simulation and experimental verification of interfacial interactions in compound squeeze cast Al/Al–Cu macro composite bimetal. T NONFERR METAL SOC. 2019; 29: 950-963.

Agrahari S, Panda I, Patel F. M, Gupta M, P. Mohanty C. Effect of cooling rate on microstructures and mechanical property of Al 1230 alloy in a sand casting process. Mater. Today: Proc. 2020; 26:1771-1775.

He C, Li Y, Li J, Xu G, Wang Z, Wu D. Effect of electromagnetic fields on microstructure and mechanical properties of sub-rapid solidification-processed Al–Mg–Si alloy during twin-roll casting. Mater. Sci. Eng. A. 2019; 766. de Souza Baptista L.A., Paradela K. G, Ferreira I. L, Garcia A, Ferreira A. F. Experimental study of the evolution of tertiary dendritic arms and microsegregation in directionally solidified Al–Si–Cu alloys castings. J. Mater. Res. Technol. 2019; 8: 1515-1521.

Campbell J. United Kingdom: Butterworth-Heinemann; 2015. 204-207 p.

Campbell F.C. United States of America: ASM International; 2012. 433-436 p.

Lazzarin, R.M, Mancin S, Noro M, Righetti G. Hybrid PCM—aluminium foams’ thermal storages: an experimental study. Int. J. LowCarbon Technol. 2018; 13: 286-291.

Sun D, Wang L. Research on heat transfer performance of passive solar collector-storage wall system with phase change materials.

Energy build. 2016; 119: 183-188.

Mousa H, Gujarathi A.M. Modeling and analysis the productivity of solar desalination units with phase change materials. Renew.

Energy. 2016; 95: 225-232.

Smithells C.J. London and United States of America: Elsevier; 2013. 941-943 p.

MatWeb. Overview of materials for Low Carbon Steel (Last visted on 20/8/2021) Crow E. L, Shimizu K. Lognormal distribution. United States of America: 1998.

Dong H. B, Lee P. D. Simulation of the columnar-to-equiaxed transition in directionally solidified Al–Cu alloys. Acta Mater. 2005; 53: 659-668.

Hadadzadeh A, Shalchi Amirkhiz B, Li J, Mohammadi M. Columnar to equiaxed transition during direct metal laser sintering of AlSi10Mg alloy: effect of building direction. Addit Manuf. 2018; 23: 121-131.

Mahapatra R.B, Weinberg F. The columnar to equiaxed transition in tin-lead alloys. METALL MATER TRANS B. 1987.

La Metallurgia Italiana - Novembre/Dicembre 2021

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Scientific papers - Die casting

Characterization of microstructural and mechanical properties of high-pressure die-cast en ac 46000 alloy M. Tocci, S. Ferri, L. Montesano, A. Pola

The present research focuses on the characterization of microstructural and mechanical properties of real castings produced by HPDC using EN AC 46000 alloy. The Cu content of the alloy was varied inside the limits prescribed by the standard for EN AC 46000 alloy to investigate the influence of Cu on the material performance and to provide results useful for industrial applications. Castings with Cu content of 2 wt.% and 4 wt.% were industrially produced using a 2500-ton HPDC machine.

Two areas of the casting with different cooling rates were selected to obtain samples for microstructural and mechanical characterization. In particular, area fraction, number density and equivalent diameter of intermetallic compounds were investigated, and the size distribution of these particles were statistically evaluated. Finally, hardness measurements and tensile tests were performed and the results were correlated to microstructural features and solidification conditions to deeply understand the alloy behavior.

KEYWORDS: HIGH PRESSURE DIE CASTING, MICROSTRUCTURE, INTERMETALLICS, TENSILE PROPERTIES INTRODUCTION Al-Si-Cu alloys are widely used for high-pressure die-casting (HPDC) processes. In particular, AlSi9Cu3 alloy (EN AC 46000) is frequently applied for the production of various components by HPDC, especially for the automotive industry. In fact, nowadays it offers many advantages, such as high productivity rate, low cost, possibility to obtain castings with complex shapes, thin walls and smooth surfaces, while the fast solidification ensures good microstructural properties. Nevertheless, the formation of porosities is a typical problem, which is emphasized in HPDC by the rapid filling able to create turbulences in the liquid metal flow. Another critical aspect from the microstructural point of view is the presence of high amounts of intermetallic particles containing Fe [1]. On the other hand, Fe has also beneficial effects in die-casting since it plays the important role of reducing the phenomenon of die soldering of the

Marialaura Tocci

Department of Mechanical and Industrial Engineering, University of Brescia, via Branze 38, 25123, Brescia

Sara Ferri

Ghial Spa, Via Giuseppe Angelo Ghidoni, 4, 25045 Castegnato BS

Lorenzo Montesano

Department of Mechanical and Industrial Engineering, University of Brescia, via Branze 38, 25123, Brescia

Annalisa Pola

Department of Mechanical and Industrial Engineering, University of Brescia, via Branze 38, 25123, Brescia

casting [2]. Several researchers deeply investigated the effect of Fe, Mn and Cr on intermetallics morphology and formation [3], while few studies examined the effect of Cu on the properties of a die-casting alloy [4,5]. In fact, the effect of Cu addition to casting alloys has mainly been studied for primary Al alloys with low Fe content [6,7] where Cu is ad-

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Memorie scientifiche - Pressocolata ded to improve mechanical properties (especially for high

46000, whose Cu content was modified inside the range

temperature applications [8]),applied in other processes, as

prescribed by the alloy standard (i.e. from 2 up to 4 wt.%).

such as gravity or low pressure die casting.

Furthermore, samples were taken from an actual casting of

Regarding the effect of Cu to a secondary AlSi9Cu3 die ca-

significant size and not from castings obtained at laboratory

sting alloy, Fabrizi et al. [4] observed a high porosity level for

scale, as usually described in scientific literature [4,9,11] to

the alloy with the highest Cu content, which is expected to

make this study as close as possible to the industrial field.

be detrimental for material performance, as discussed also

The aim is to quantify the influence of Cu content on micro-

by other researchers [9]. Instead, Outmani at el. [5] found

structural features (especially intermetallic phases and po-

that, despite the high porosity, the alloy with the highest Cu

rosity level) and mechanical properties.

content (approximately 3 wt.%) showed enhanced tensile strength. Similar effect of Cu was documented also by Lu-

EXPERIMENTAL PROCEDURE

mley et al. [10]. It has to be mentioned that in these studies

The present study was carried out on castings obtained by

several parameters were changed, as the content of other al-

HPDC process with EN AC 46000 alloy (often indicated as

loying elements, injection temperature and pressure [5,10]

AlSi9CuFe alloy). Five castings with the minimum (i.e. ap-

and therefore it is difficult to clearly identify the role of Cu.

proximately 2 wt. %) and maximum Cu content (i.e. approxi-

For these reasons, it is believed that further studies on this

mately 4 wt. %) allowed for EN AC 46000 alloy were produ-

topic are necessary to exploit the alloy performance from

ced. The chemical composition of the final castings is shown

both a scientific and industrial point of view. Therefore, the

in Table 1, as obtained from measurements by optical emis-

present research focuses on the commercial alloy EN AC

sion spectrometer.

Tab.1 - Mean chemical composition of the final castings.

Alloy

Si

Cu

Fe

Mn

Mg

Cr

Ni

Zn

Pb

Al

Cu2

8.025

2.097

1.097

0.296

0.125

0.094

0.095

0.918

0.058

Bal.

Cu4

8.298

4.104

1.033

0.231

0.149

0.095

0.111

1.031

0.089

Bal.

The sludge factor was calculated for both the alloys [12], as

order to evaluate different cooling conditions for each al-

In addition, the area fraction of sludge that can form in the

corresponds to the warmer zone (i.e. which solidifies more

well as the critical temperature for sludge formation [12]. holding furnace was evaluated [13]. Samples for micro-

structural and mechanical characterization were taken from two different positions in the casting (indicated in Fig. 1) in

loy. In particular, the position A is located near the gate and slowly), while the position B is located opposite to the gate

and corresponds to the coldest zone (i.e. which solidifies faster).

Fig.1 - Picture of the casting used for the present study with indication of the analyzed areas.

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Scientific papers - Die casting The microstructure of samples was observed by means of

an optical microscope Leica DMI 5000 M, equipped with LAS image analyzer, on mirror polished samples. Average secondary dendrite arm spacing (SDAS) was calculated

for each sample, according to the linear intercept method.

Furthermore, porosity level was calculated by digital image analysis on a total area of 15 mm for each sample.

2

The main phases and intermetallic compounds present

in the samples were characterized by means of a scanning electron microscope (SEM), LEO EVO 40 equipped with

an Energy Dispersive Spectroscopy (EDS) probe for elemental analysis. Digital image analysis was carried out on twenty SEM images (backscattering mode) for each alloy for both the positions considered in order to evaluate the area

fraction, equivalent diameter, and number density (number

of particles per unit of area) of intermetallic particles. Results in terms of equivalent diameter of these particles were further statistically evaluated by means of JMP® software.

Finally, tensile specimens were machined to final shape according to UNI EN ISO 6892-1 standard (sample diameter of

4 mm and gauge length of 20 mm). Tensile tests were carried out with a Galdabini Quasar testing machine at room tempe-

rature. The elongation was measured using a knife-edge ex-

tensometer fixed to the gauge length of the specimens. The crosshead speed was set at 3 mm/min in the elastic field and at 9 mm/min in the plastic one. Three samples were tested for each condition and average and standard deviation were

calculated for ultimate tensile strength (UTS), yield strength (YS) and elongation (El. %) values extrapolated from strain-

perature of the holding furnace (675 °C) was slightly below the critical temperature for sludge formation (687 °C for

Cu2 alloy, 682 °C for Cu4 alloy), suggesting the likely for-

mation of primary intermetallic particles in the furnace. This

is consistent with the calculation of sludge area fraction in the casting, which is estimated to be approximately 1%.

This represents a limited area fraction of primary intermetallic particles, which nevertheless has to be considered to thoroughly understand material performance. Finally, ac-

cording to the charts reported by various authors [12,15], no sedimentation of sludge in holding furnace is expected.

Regarding microstructural properties, the SDAS values in

position A are slightly higher than in position B for both the alloy compositions (Table 2). It follows that in the former case the solidification rate is lower than in the latter and, ea-

sily leading to different mechanical properties. In addition, in Table 2, porosity level is indicated as measured from di-

gital image analysis. Interestingly, it was found that the average porosity of sample Cu4-A is only slightly higher than

Cu2-A, despite the higher Cu content. On the other hand, Cu4-B samples is characterized by the highest porosity level (above 1 %), suggesting that in this case the formation

of eutectic intermetallic phases due actually hindered liquid feeding leading to significant microporosity formation. The

faster solidification, due to the colder zone, combined with

the higher distance from the gate, hindered the effect of pressure in compensating shrinkage and filling the interdendritic regions, giving rise to high porosity.

stress curves. Based on tensile tests results, the Quality Index, frequently used in foundry, was calculated as indicated

by Drouzy et al. [14].

RESULTS

First, the sludge factor was calculated for both the alloys and values in the range 1.8-2 were found. In addition, the tem-

Tab.2 - Average values of SDAS and porosity for the studied samples.

Sample

Cu2-A

Cu2-B

Cu4-A

Cu4-B

SDAS (μm)

19 ± 2

13 ± 3

20 ± 1

16 ± 1

Porosity (%)

0.55 ± 0.10

0.20 ± 0.05

0.65 ± 0.20

1.25 ± 0.30

For each sample, various intermetallic particles were also identified and analyzed using SEM-EDS (Fig. 2).

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Fig.2 -SEM images and intermetallics identification for a) Cu2-A, b) Cu2-B, c) Cu4-A and d) Cu4-B samples.

Results from digital image analysis shown in Table 3, in terms of area fraction and number density of intermetallic particles, supported the evaluation of the presence of intermetallic particles.

Tab.3 - Analysis of intermetallic particles in the studied samples.

Sample Area fraction (%) Particles density (particles/mm²)

Cu2-A

Cu2-B

Cu4-A

Cu4-B

4.1

4.6

8.2

6.0

2.8 ·103

2.9 ·103

4.9 ·103

3.5 ·103

For Cu2 alloy, the different cooling conditions between position A and B do not significantly affect the total amount of

intermetallic particles since area fraction and particles den-

sity are comparable. On the other hand, the increase in Cu content leads to a higher area fraction of intermetallics than for alloy Cu2, especially in position A where the area fraction is the double in comparison with samples Cu2-A. Intere-

stingly, for sample Cu4-B the area fraction of intermetallic particle is reduced. This can be ascribed to the different co-

oling conditions of the analyzed samples. In position A, based on SDAS measurements, it is expected to have a lower

evaluation of the size of intermetallic particles was carried

out in terms of equivalent diameter of the particles. In this regard, it is reported that that the size of intermetallic particles follows a two-parameters lognormal distribution [16].

This was verified also in the present study, as shown in Fig. 3,

where the lognormal probability density function was used to fit experimental data of equivalent diameter obtained by

digital image analysis. The shape parameter μ and the scale

parameter σ, estimated from lognormal distribution are also indicated.

solidification rate, and this allows intermetallic particles to

grow, resulting in the observed high area fraction. Further

La Metallurgia Italiana - Novembre/Dicembre 2021

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Scientific papers - Die casting

Fig.3 - Experimental data and relative lognormal fitting for intermetallic particles in the studied samples as a function of equivalent diameter: a) Cu2-A, b) Cu2-B, c) Cu4-A and d) Cu4-B samples.

It can be observed that particles size distribution is quite

limited sludge factor (SF = 1.8-2). This is also consistent

similar for all the investigated conditions and that most

with the limited expected sludge area fraction (approxi-

particles have an equivalent diameter below 6 μm. Ac-

mately 1 %, as above-mentioned), while the total area

cording to [17], these can correspond to proeutectic in-

fraction of intermetallic particles ranges from 4 to 8% in

termetallic particles, as opposed to primary sludge par-

the investigated samples (Tab. 3).

ticles, which are characterized by bigger size. This is not

Tensile properties of the studied alloy are shown in Fig. 4.

surprising since the studied alloys are characterized by a

Fig.4 - Tensile properties of studied samples.

Samples with low Cu content exhibit quite similar va-

The loss in UTS and elongation for Cu4-A sample can

lues of tensile strength. This is consistent with the simi-

be explained considering that this sample is characteri-

lar content of intermetallic particles, while the minimum

zed by the highest area fraction of intermetallic particles,

amount of porosity for sample Cu2-B may be responsible

which have a brittle behavior and easily detach from the

for its slightly higher elongation. When Cu4 alloy is con-

Al matrix during tensile testing. The poor performance of

sidered, it appears that ductility is significantly reduced

Cu4-B samples, despite the lower number of intermetal-

and that also UTS is decreased, even if not so strongly.

lic particles, is instead related to the high porosity level,

On the other hand, an increase in YS can be appreciated.

which diminishes the load bearing area of the samples,

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Memorie scientifiche - Pressocolata resulting in reduced UTS and ductility of the material. Re-

produced by HPDC using AlSi9Cu alloy. The Cu content

garding YS, it has to be mentioned that the castings are

of the alloy was changed from 2 wt.% to 4 wt. % in order

cooled in water after extraction from the die. This ope-

to investigate the influence of Cu on the material perfor-

ration can act as an effective quenching, resulting in hi-

mance and to provide results useful for industrial applica-

gher amount of Cu retained in solid solution for Cu4 alloy,

tion. It was found that the increase in Cu content leads to

due to excess of Cu in comparison with Cu2 alloy. This

a higher total area fraction of intermetallic particles, while

can lead to a higher amount of Cu in solid solution, which

their size distribution is not affected by Cu content and

is effective in hindering dislocation motion during tensi-

cooling rate. As a result, Cu4 alloy exhibits lower tensile

le testing. This results in the enhanced YS of Cu4 alloy.

strength and ductility, especially in position B, where the

Tensile behavior of the studied samples is summarized by

presence of intermetallic particles was coupled to high

the quality index, which has the highest values for Cu2-A

the porosity level. This is correlated to the cooling condi-

samples, while it is significantly reduced for Cu4 alloy.

tions of the considered position in the casting, as indicated by SDAS values. On the other hand, higher Cu content

CONCLUSIONS

lead to improved yield strength likely because of higher

The present study focuses on the characterization of mi-

Cu retained in solid solution.

crostructural and mechanical properties of real castings

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17]

J.A. Taylor, Iron-containing intermetallic phases in Al-Si based casting alloys, Proc. Mater. Sci. 1 (2012) 19-33.

Z.W. Chen, M.Z. Jahedi, Die erosion and its effect on soldering formation in high pressure die casting of aluminium alloys, Mater. Des. 20-6 (1999) 303-309.

H. Yang, S. Ji, Z. Fan, Effect of heat treatment and Fe content on the microstructure and mechanical properties of die-cast Al-Si-Cu alloys, Mater. Des. 85 (2015) 823-832.

A. Fabrizi, S. Ferraro, G. Timelli, The influence of Sr, Mg and Cu addition on the microstructural properties of a secondary AlSi9Cu3(Fe) die casting alloy, Mater. Char. 85 (2013) 13-25.

I. Outmani, L. Fouilland-Paille, J. Isselin, M. El Mansori, Effect of Si, Cu and processing parameters on Al-Si-Cu HPDC castings, J. Mater.

Process. Technol. 249 (2017) 559-569.

Y. Zheng, W. Xiao, S. Ge, W. Zhao, S. Hanada, C. Ma, Effects of Cu content and Cu/Mg ratio on the microstructure and mechanical properties of Al-Si-Cu-Mg alloys, J. Alloys Compd. 649 (2015) 291-296.

S. Seifeddine, E. Sjölander, T. Bogdanoff, On the Role of Copper and Cooling Rates on the Microstructure, Defect Formations and Mechanical Properties of Al-Si-Mg Alloys, Materials Sciences and Applications 4 (2013) 171-178.

A.M.A. Mohamed, F.H. Samuel, S. Al Kahtani, Microstructure, tensile properties and fracture behavior of high temperature Al–Si–Mg– Cu cast alloys, Mat. Sci. Eng. A 577 (2013) 64-72.

S.G. Shabestari, H. Moemeni, Effect of copper and solidification conditions on the microstructure and mechanical properties of Al–Si– Mg alloys, J. Mater. Process. Technol. 153-154 (2004) 193-198.

R.N. Lumley, R.G. O'Donnell, D.R. Gunasegaram, T. Kittel-Sherri, M. Gershenzon, A.C. Yob, I.J. Polmear, The role of alloy composition in the heat treatment of aluminium high pressure die castings, Metall. Sci. Techn. 26 (2008) 2-11.

X.Y. Jiao, J. Wang, C.F. Liu, Z.P. Guo, G.D. Tong, S.L. Ma, Y. Bi, Y.F. Zhang, S.M. Xiong, Characterization of high-pressure die-cast hypereutectic Al-Si alloys based on microstructural distribution and fracture morphology, J. Mater. Sci. Technol. 35 (2019) 1099-1107.

S.G. Shabestari, The effect of iron and manganese on the formation of intermetallic compounds in aluminum–silicon alloys, Mat. Sci. Eng. A 383 (2004) 289–298.

S. Ferraro, G. Timelli, Influence of Sludge Particles on the Tensile Properties of Die-Cast Secondary Aluminum Alloys, Metall. Mater.

Trans. B 46B (2015) 1022-1034.

M. Drouzy, S. Jacob, M. Richard, Interpretation of tensile results by means of Quality Index and probable yield strenth, International cast metals journal 5-2 (1980) 43-50.

S. Ferraro, A. Bjurenstedt, S. Seifeddine, On the Formation of Sludge Intermetallic Particles in Secondary Aluminum Alloys, Metall.

Mater. Trans. A 46A (2015) 3713-3722.

M. Tiryakioğlu, Si particle size and aspect ratio distributions in an Al-7%Si-0.6%Mg alloy during solution treatment, Mat. Sci. Eng. A 473-1-2 (2008) 1-6.

S. Ferraro, A. Fabrizi, G. Timelli, Evolution of sludge particles in secondary die-cast aluminium alloys as function of Fe, Mn and Cr, Mater. Chem. Phys. 153 (2015) 168-179

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Scientific papers - Die casting

Alternative alloying concepts of hot work tool steels for application in die casting P. Niederhofer, F. van Soest, M. Gürcan, H.-G. Krull, T. Schneiders

High performance hot work tool steels need to feature complex mechanical and physical properties in order to fulfill the requirements arising from different die casting applications. The required properties depend i.a. on the die casting process and the materials to be cast. They may include e.g. high toughness and strength at elevated temperature in order to be able to withstand thermal shocks occurring during high-pressure die casting. For application in low-pressure die casting, high temperature stability can be important in order to maintain mechanical properties even after long exposure to molten metal. In terms of physical properties, a high thermal conductivity is of particular interest, since on the one hand it increases resistance to thermal shocks, while on the other hand it can help to accelerate cooling of cast parts and thus in turn reduce the process cycle time. In this contribution, different new alloying concepts are presented. These include a specifically developed CrMoV-alloyed hot work tool steel featuring an optimized combination of high temperature strength, toughness, and resistance to thermal shock. A second new development combines superior thermal conductivity, high temperature stability, and high resistance to thermal shock. Furthermore, an additional approach makes use of the beneficial properties of a bainitic microstructure, which results in a combination of high strength at elevated temperatures and high toughness at minor alloying cost. Relevant properties of the alternative alloying concepts are compared to those of standard hot work tool steels, which are conventionally used in die casting applications.

KEYWORDS: DIE CASTING, TOOL STEEL, THERMAL SHOCK, TEMPERATURE STABILITY, THERMAL CONDUCTIVITY, HIGH-TEMPERATURE STRENGTH, TOUGHNESS, MICROSTRUCTURE INTRODUCTION During (high pressure) die casting ((HP)DC) of non-ferrous metals like e.g. Al- or Mg-alloys, different environmental conditions occur, which can affect dies and tool steels used for said application. These may include exposure to elevated temperatures due to contact with molten metal for longer duration as well as fast cycles of high and low temperatures due to spray cooling between two parts in HPDC. Furthermore, liquid metal injected with high velocity into the cavities of the die can cause mechanical stresses as well as occurrence of erosive wear (1). In turn, this means that tool steels used for die casting, depending on process parameters, need to exhibit different properties in order to ensure a proper service life.

In the case of low pressure die casting, maintenance of service hardness even during long exposure to elevated temperatures is of particular interest. This is ensured by high

P. Niederhofer

Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Auestraße 4, 58452 Witten, Germany (philipp.niederhofer@dew-stahl.com)

F. van Soest

Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Oberschlesienstraße 16, 47807 Krefeld, Germany

M. Gürcan

Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Oberschlesienstraße 16, 47807 Krefeld, Germany

H.-G. Krull

Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Oberschlesienstraße 16, 47807 Krefeld, Germany

T. Schneiders

Deutsche Edelstahlwerke Specialty Steel GmbH & Co. KG, Auestraße 4, 58452 Witten, Germany

microstructural stability, which means resistance to e.g. coarsening of carbides.

In addition, during high pressure die casting, which is fre-

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Memorie scientifiche - Pressocolata

quently characterized by the intention to produce a large

EXPERIMENTAL

amount of pieces in short cycle times, dies can be stres-

The chemical composition of the investigated special

sed by frequent changes in temperature featuring quite

tool steels as well as reference materials is listed in Tab. 1.

large amplitudes (thermal shock), which results in mecha-

Thermodur E 40 K Superclean is based on a conventional

nical stresses. In consequence, as explained by the theory

5 mass% chromium hot work tool steel and is characteri-

of Kindbom (2), the formation of cracks is inevitable (heat

zed mainly by addition of 2 mass% molybdenum as well as

checking). However, different material properties can con-

low silicon content and lowest amounts of tramp elemen-

tribute to delay of formation or propagation of cracks (3).

ts. In combination with the vanadium content, it features an

These include high strength and toughness at elevated tem-

optimized combination of high-temperature strength and

peratures, since it increases resistance to thermally induced

toughness. Thermodur 2383 Supercool was originally de-

plastic deformation (1) (2) (3) (4). A low coefficient of thermal

veloped for application in hot stamping tools. Due to the

expansion could also be favorable (3), however, in steel it

well-balanced chemical composition, which mainly features

depends on alloying content. Thus, since for economical re-

the lack of chromium and silicon, it is characterized by very

asons it is virtually undesired to further increase the conten-

high thermal conductivity yet still showing good mechani-

ts of alloying elements in hot work tool steels significantly,

cal properties. Thermodur 2322 exhibits a bainitic instead of

this option is rather theoretical. Furthermore, a high thermal

a martensitic microstructure, which results in a good com-

conductivity is beneficial since it can reduce thermal stres-

bination of high toughness and remarkable strength at ele-

ses during HPDC due to faster compensation of temperatu-

vated temperature. Furthermore, in deviation from all other

re differences (3) (5) (6) (7) (8). Basically, thermal conducti-

hot work tool steels investigated in this study, 2322 was not

vity of steel is linked with the amount of lattice defects, the

electroslag-remelted (ESR). Specimens were taken from

most severe of which are alloying elements in solid solution.

transition areas of large blocks and heat treated. Parameters

Thus, reduction of alloying contents can increase thermal

were chosen from preliminary investigations on tempering

conductivity, and additionally save cost. However, they are

behavior as shown in Fig. 2. Consequently, the following

important for aforementioned mechanical properties. Cr for

investigations were performed. Toughness (Charpy-V as

example, which is known to be highly detrimental to heat

well as unnotched specimens), tensile testing, and thermal

conduction of steel (9), cannot be neglected in some cases

shock resistance (self-constructed test rig, details i.a. in (3)

e.g. dies featuring large cross-sections, which need to exhi-

as shown in Fig. 1). The latter allows for thermal cycling of

bit uniform hardness distribution (through hardenability) (8),

specimens between inductive heating and a cooling bath,

which is ensured by addition of chromium. Consequently,

which was performed from 2,000 up to 8,000 cycles, fol-

choosing tool steels featuring the required properties based

lowed by microscopic evaluation of cracking (number and

on analysis of process parameters allows for optimized re-

length of cracks).

sults.

Thus, the use of common premium hot work tool steel grades like e.g. 1.2343, 1.2344 or 1.2367 may result in sufficient service life of dies in many cases. However, there can be applications where, based on a systematical analysis of parameters and conditions, significant improvements can be achieved by using special hot work tool steels, which in turn may tentatively feature rather unconventional alloying concepts.

In this contribution, recently developed special tool steels are presented focusing especially on their properties related to application in die casting.

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Scientific papers - Die casting

Tab.1 - Chemical analysis of investigated materials in mass%.

STeel Grade

C

Si

Mn

Cr

Mo

Ni

V

Others

Thermodur E 40 K Superclean

0.36

0.3

0.3

4.8

1.8

-

0.8

+

Thermodur 2383 Supercool

0.45

-

0.9

-

1.5

0.9

1.5

-

Thermodur 2322

0.18

0.55

0.8

2.0

0.7

0.2

0.1

+

Thermodur 2343 Superclean

0.37

1.0

0.4

5.3

1.3

-

0.4

-

Thermodur 2344 Superclean

0.4

1.0

0.4

5.3

1.4

-

1.0

-

Thermodur 2367 Superclean

0.37

0.3

0.4

5.0

3.0

-

0.6

Fig.1 - Test rig for determination of heat checking resistance.

Furthermore, thermal conductivity was determined by me-

600 °C when compared to 1.2343, which indicates high mi-

ans of indirect method, which included measurement of

crostructural stability in the case of E 40 K as well. Because

thermal diffusivity (laser flash analysis), specific heat capaci-

of the different alloying systems, 1.2383 and 1.2322 show

ty (differential scanning calorimetry), and density (buoyancy

different tempering behavior. The first exhibits significantly

principle, dilatometry). Multiplication of said values, which

more intense secondary hardening behavior, which in addi-

all depend on measurement temperature, results in thermal

tion is shifted to higher temperatures, which in turn means

conductivity.

that 1.2383 at temperatures above 650 °C shows the highest hardness. The latter in contrast features significantly lower

RESULTS AND DISCUSSION

hardness in the secondary hardness maximum region, but it

Tempering behavior

seems noticeable, that the hardness drop at higher tempe-

Fig. 2 shows on the left side the tempering curves of the in-

ratures is less pronounced as compared to conventional hot

vestigated special hot work tool steels in the region of se-

work tool steels.

condary hardness maximum. While it becomes clear that 1.2344 exhibits the highest secondary hardness due to increased amounts of carbon and vanadium, the hardness peaks of 1.2343 and 1.2367 are slightly lower. The latter shows increased hardness at temperatures above approximately 600 °C, which means less hardness decrease due to higher microstructural stability. E 40 K features slightly lower secondary hardness but comparable values above La Metallurgia Italiana - November/December 2021

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Memorie scientifiche - Pressocolata

Fig.2 - Tempering behavior of investigated special hot work tool steels.

Long-term tempering behavior

shows quite comparable endurance, but at a lower level of

As shown in Fig. 2 on the right side, microstructural stabi-

hardness, which, for some applications however may be

lity of the special hot work tool steels was investigated by

sufficient.

performing tempering experiments for longer durations at 600 °C. The specimens were either used in quenched and

Strength and toughness at elevated temperatures

double tempered (“qt”, all except of 1.2322) or just quen-

As can be derived from Fig. 3, both tensile strength as well

ched (1.2322) to 45 HRC condition. In the case of tempering

as toughness (Charpy-V) testing were performed at 600 °C

to 45 HRC, this means that temperatures larger than 600 °C

in order to illustrate the properties at elevated temperatures.

were applied prior to long-term tempering. Thus, the ini-

Results described in the following were obtained using spe-

tial tendency for microstructural changes during long-term

cimens heat treated as described before except of 1.2322,

tempering at 600 °C is reduced due to qt. By trend, the ten-

which was used in qt condition as well. It becomes obvious

dencies seen in the tempering curves shown in Fig. 2 are

that 1.2383 and 1.2367 exhibit highest strength at this tempe-

confirmed. After 30 h of testing, 1.2343 and 1.2344 show si-

rature, which once again underlines their high microstructu-

milar hardness, while that of E 40 K is slightly higher. Due to

ral stability, which has already been indicated. However, the

higher microstructural stability, 1.2367 shows less decrease

differences in strength are quite low. Especially 1.2322, whi-

in hardness, while 1.2383 exhibits the best results expressed

ch features lower hardness and thus strength in qt condition

by lowest reduction of hardness by long-term tempering.

at room temperature, shows quite high strength at 600 °C.

Because of the lack of tempering, 1.2322 features highest re-

The same holds true for the high temperature toughness,

duction of hardness at longer exposure to 600 °C. However,

which is remarkably high in the case of 1.2322, while the re-

when comparing the inclination of curves of the investigated

ference materials exhibit slightly lower values.

materials at durations between 10 and 30 h, these seem to be quite comparable. Thus it can be concluded, that 1.2322

Fig.3 - Strength and toughness at elevated temperature.

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Scientific papers - Die casting

Thermal conductivity

ased thermal conductivity (Fig. 4), while, as already descri-

While, as already mentioned, a reduction in coefficient

bed, showing good mechanical properties. E 40 K, like the

of thermal expansion would require significantly higher

conventional 5 % chromium hot work tool steels, features

amounts of alloying contents than hot work tool steels

lower values of heat conduction, yet, similar to 1.2367, they

usually have, thermal conductivity can be influenced more

are slightly increased as compared with 1.2343 and 1.2344,

unpretentiously. Due to the optimized alloying concept,

respectively.

1.2383 at similar hardness level shows considerably incre-

Fig.4 - Thermal conductivity of investigated special hot work tool steels.

Heat checking resistance

quently by a comparatively high value of total crack depth.

As already described, resistance to thermal shock, which is a

The lowest crack depth among the reference alloys in this

crucial property especially in the case of hot work tool steels

study can be seen in the case of 1.2343, which shows similar

applied in high pressure die casting, was investigated as well.

values compared to E 40 K after 8,000 cycles. The difference

The results are shown in Fig. 5. The evaluation of specimen

between these two grades is, that E 40 K shows more, but

was performed by counting the number of cracks as well as

less deep cracking. Even more cracks were discovered in

measuring their length in the cross-section of a predefined

the case of 1.2383, however, these were exceptionally short,

surface area. By trend, when focusing on the longest test du-

thus resulting in a small total crack depth. In contrast, 1.2322

ration (8,000 temperature cycles) the following conclusions

shows occurrence of less but deeper cracks, thus resulting

can be drawn, taking a certain measurement uncertainty of

in a considerably small total depth of cracks as well. The

the test setup into account. The reference materials 1.2343,

very good heat checking resistance of special steels 1.2383,

1.2344, and 1.2367 can be considered as showing quite com-

1.2322, and E 40 K can be explained by the improved thermal

parable behavior, which is characterized by formation of si-

conductivity of the first and second, respectively, while the

milar numbers of cracks (little less in the case of 1.2343) that

latter shows an optimized combination of high temperature

exhibit approximately the same maximum depth and conse-

strength and toughness.

Fig.5 - Heat checking resistance of investigated special hot work tool steels.

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Memorie scientifiche - Pressocolata CONCLUSIONS

ty, high temperature stability, and high resistance to ther-

In this study, different special hot work tool steels were

mal shock. In an additional approach, a bainitic hot work

characterized with special focus on properties relevant

tool steel (1.2322) was developed, which, based on the

for application in die casting. A specifically developed Cr-

beneficial properties of this kind of microstructure, resul-

MoV-alloyed hot work tool steel (E 40 K) features an op-

ts in a combination of high strength at elevated tempera-

timized combination of high temperature strength, tou-

tures and high toughness at minor alloying cost. Thus, the

ghness, and resistance to thermal shock compared with

alloying concepts presented are suitable for application

conventional hot work tool steels. A second new deve-

in various die casting processes, which will be verified by

lopment (1.2383) combines superior thermal conductivi-

industrial trials.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9]

Berns, H. Beispiele zur Schädigung von Warmarbeitswerkzeugen. HTM - Zeitschrift für Werkstoffe, Wärmebehandlung, Fertigung.

2004, 6, p. 379-387.

Kindbom, L. Warmrissbildung bei der Temperaturwechselbeanspruchung von Warmarbeitswerkzeugen. Archiv Eisenhüttenwesen.

35, 1964, Vol. 8, p. 773-780.

Ehrhardt, R., et al. Improving the Heat Checking Characteristics of AISI H13 by Modification of the Chemical Composition. Die Casting Engineer. 2003, p. 30-37.

Schneiders, T. e Gürcan, M. THERMODUR E 40 K SUPERCLEAN – ein Warmarbeitsstahl mit verbesserter Zähigkeit für Druckgussanwendungen. BHM Berg- und Hüttenmännische Monatshefte. 162, 2017, Vol. 3, p. 101-109.

Valls, I., Casas, B. e Rodriguez, N. Importance of Tool Material Thermal Conductivity in the Die Longevity and Product Quality in HPDC. 8th International Tooling Conference 2009 - Proceedings. 2009, p. 127-140.

Eliasson, L. e Sandberg, O. Effect of Different Parameters on Heat-Checking Properties of Hot-Work Tool Steels. 2nd Tool Conference 1989 - Proceedings. 1989, p. 3-14.

Ayabe, M., et al. Effect of High Thermal Conductivity Die Steel in Aluminum Casting. International Journal of Metalcasting. 2008, 2, p.

47-55.

Caliskanoglu, D. Einfluss der Legierungslage auf das Anwendungspotential temperaturwechselbeanspruchter Warmarbeitsstähle, Dissertation. Leoben : Montanuniversität, 2002.

Terada, Y., et al. Effects of Alloying Additions on Thermal Conductivity of Ferritic Iron. ISIJ International. 42, 2002, 3, p. 322-324.

La Metallurgia Italiana - Novembre/Dicembre 2021

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Scientific papers - Die casting

CS1 - The new hot-work tool steel for die casting dies with the highest surface requirements Dr. E.Meurisse, I.chruff

The number of parts produced by die casting is increasing permanently. Furthermore, the diversity and the complexity of cast parts is growing higher. The products are not only larger, but also more complicated in their design. Economical die casting requires dies which allow continuous production without any unscheduled downtimes. This depends not only on a proper die design. The properties of the used hot-work tool steels are adjusted in order to fulfill the prevailing requirements and have a considerable impact, too. Consequently, the die casting industry has increasing demand of hot-work tool steels with specifically combined properties. Particularly the demand on the surface quality of end products is continuously increasing. In order to meet the new demands of the die casting market, Kind&Co has developed a new hot-work tool steel.

This new steel is able to offer a working hardness of up to 56 HRC. At the same time, it has a very high toughness potential at such a high hardness. This high toughness potential of the new special hot-work tool steel leads to an outstanding resistance against thermal cracking. This premium grade – CS1 – has contributed to performance improvement of up to 600 %.

This paper presents the properies of CS1 and shows several examples of successful application.

KEYWORDS: PREMUIN STEEL CS1, HPDC, THERMAL SHOCK RESISTANCE, TOUGHNEES, INDUSTRIAL TRIALS

INTRODUCTION Die cast components gain more and more importance in our daily life. The die casting process permits economical manufacturing of a diverse array of components including household articles, cases for electronic instruments or structural parts of cars. Surface quality in automotive is becoming increasingly important especially for components for e-mobility or structural parts. Due to the safety relevance of many structural parts, these parts must be free of surface defects. These defects like burrs or spots could initiate cracks. Furthermore, assembling and sealing surfa-

Dr. Emeline Meurisse, Ingolf Schruff

Kind & Co., Edelstahlwerk, GmbH & Co., KG, Wiehl, Germany

ces require perfect condition in order to guarantee proper functions [1]. Beside the automotive industry, the communication industry with a growing market of the 5G devices is a futher driving force for the development in the die casting application. Projections from CCS Insight indicates that global 5G connections will exceed 1 billion in 2022, surging to 3,2 bllions in 2025 [2]. Triggered by the boom in 5G technology, cost effective die cast components with a high

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Memorie scientifiche - Pressocolata

quality are required. For example cast heatsinks represent a

products. An increase in hardness can positively influence

major challenge for the foundries. These cast products are

the thermal shock resistance as an augmentation of the har-

often used without additional finishing, although they inclu-

dness generates an increase of the tensile strength as well

de a lot of functionalities like cooling fins, mounting holes

as of the fatigue strength [3]. At the same time, however, the

and fasteners. Therefore the highest demands are placed on

toughness of the steel decreases and the risk of cracks rises.

the surface quality and geometrical accuracy, defects on the

For this reason, for example, the hardness of a die made of

die surface as shown in Figure 1 have to be avoided.

hot-work tool steel type 1.2343 should not be set to over

It is therefore recommended to use hot-work tool steels

47 HRC without consulting the tool steel manufacturer. The

with highest thermal shock resistance as die material in or-

newly developed premium hot-work tool steel CS1 allows

der to noticeably delay the formation of thermal shock crack

a hardness in use of up to 56 HRC, which leads to a further

networks. These crack networks also make the ejection the

improvement in thermal shock resistance.

cast parts more difficult and can in the worse case deform the

Fig.1 - Typical appearance of thermal shock cracks on the surface of a HPDC die during magnetic particle inspection.

CS1 - THE NEW PREMIUM HOT-WORK TOOL STEEL

duced. The well balanced alloying concept with increased

The complex loads to which die castings dies are exposed

contents of C, Mo and Nb compared to 1.2343 combined

in the process consist of chemical, mechanical, cyclic and

with an accurante production allows to achieve an optimale

thermal components. Because of these different loads,

properties profil. In order to respect the high demands con-

the hot-work tool steels used in die casting applications

cerning homogeneity and toughness, the premium steel

must combine various properties in an optimal way. Besi-

CS1 is exclusively produced by eletcro-slag-remelting pro-

de excellent thermal shock resistance a high strength and

cess.

fatigue strength at elevated temperature, a good tempering

The higher C-content confers the premium steel CS1 the

resistance, a high toughness potential and a sufficient ther-

highest secondary hardness maximum of 58 HRC (Figure 2,

mal conductivity are required. In order to cover the different

left). In comparison with the standard grades USN (1.2343)

requirements for die casting, Kind&Co developed the pre-

and USD (1.2344) the secondary hardness maximum of CS1

mium hot-work tool steel CS1.

is 3 to 4 HRC higher.

The premium steel CS1 is a 5%-Cr alloyed hot-work tool steel based on the principle of highest puritiy. The concentrations of P and S as weel as the concentration of detrimental elements like B or Sn have been drastically re-

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Scientific papers - Die casting

Fig.2 - Tempering curves of the discussed steels (left) / Long-time tempering of USN and CS1 (right).

Furthermore the grade CS1 shows an excellent resistance

a clearly better long-time tempering resistance than USN

against tempering and thus against undesired softening du-

and the risk of softening in use is reduced with CS1.

ring casting operation. This is confirmed by the results of

A futher important property is the high-temperature stren-

long-time tempering tests (Figure 2, right). Samples, which

gth. A good high-temperature strength allows to withstand

were previously quenched and tempered to a hardness of 50

the thermal loads of the HPDC process. Depending on the

HRC, were kept at different temperatures between 10 h and

process, the temperature at the die surface can achieve e.g.

50 h. Hardness measurements demonstrate that long-time

500°C for a short while with each shot. As shown in Figure

tempering at 540 °C does not affect the hardness. A tempera-

3 (left), the tested steels have a similar yield strength up to

ture of 580°C leads to only moderate hardness loss. At tem-

400°C. At higher temperature the benefit of CS1 is evident.

peratures above 600°C, the hardness is significally reduced.

Furthermore the premium grade develops a higher hard-

In comparison with the steel USN, the decrease of hardness

ness and allows to apply a hardness up to 56 HRC depending

is considerably slower. While the hardness of USN drops to

on the process. The increase in hardness provides the steel

40 HRC after only 10 hours on 620°C the grade CS1 achieves

CS1 an even better strength (Figure 3, right).

this level after 20 hours on the same temperature. CS1 offers

Fig.3 - Values of the 0,2% Yield strength Rp0,2 of the discussed steels as function of the test temperature All samples hardened + tempered to Rm = 1450 MPa (45 HRC) (left) / Influence of hardness on the high-temperature strength of CS1 (right).

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In addition to high-temperature strength and hardness, the

of 230 mm). The impact energy values measured on ISO-V-

toughness of hot-work tool steels dedicated to die casting is

notch samples are given in Figure 4. With 23 J, CS1 surpasses

important in order to withstand the sudden mechanical and

significantly the NADCA-requirements for the grade 1.2344

thermal loads during the HPDC process without breaking.

(at 45 HRC). Although higher hardness generally reduces

The toughness was tested after a heat treatment in the labo-

toughness, CS1 is even able to achieve impact energy values

ratory according to the NADCA-rules and at different hard-

of 15 J (NADCA level for 1.2344 at 45 HRC) up to a hardness

ness values (material was taken from a bar with a diameter

of 58 HRC.

Fig.4 - Impact toughness of CS1 at different hardness (short transverse orientation).

HEAT TREATMENT RECOMMENDATION FOR DIES

with greater safety in the core. The pearlitic transformation is

In order to adjust the properties, each die casting die must

postponed to longer time in comparison to steels like 1.2343

be hardened and tempered. Figure 5 displays the CCT-dia-

and 1.2344 in the same way. In order to consistently achieve

gramm of CS1 for a hardening temperature of 1030°C. The

a martensitic microstructure a wider band of quenching ra-

undesired bainite transformation takes place after 60 minu-

tes compared to 1.2343 can be applied and thus lower risk of

tes, whereas the bainitic transformation starts already after

transformation-induced cracks.

10 mintes. CS1 shows an outstanding through-hardenability. The comparably late beginning of the undesired bainitic transformation allows dies to be hardened martensitically

Fig.5 - Continuous time-temperature-transformation diagrams of CS1 (left) and USN (1.2343) (right).

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Scientific papers - Die casting

APPLICATION RESULTS

achieve 24000 shots. The lifetime of the dies was improved

As shown before, it is possible to apply a higher hardness

up to 600 % and a constant productivity could be achieved

with the steel CS1 in comparison to standard steels. Ne-

thanks to the use of CS1.

vertheless the choice of the hardness depends on the di-

A second example is a throttle body (Figure 6 middle). For

mension, the geometry and the complexity of die. In the

this piece, the high surface requirements demanded exces-

following section some application examples of CS1 with a

sive remachining of die made of 1.2343, resulting in a maxi-

hardness above 50 HRC will be presented.

mum life of 90000 shots. In the tested application the final

The first application example is a motorcycle brake lever

customer did not tolerate any mark of thermal shock cracks

holder (Figure 6 left). The surface demand of this visible part

in the sealing areas.

is very high, cracks in the die insert are not allowed. Even

A trial with CS1 as die material with a hardness of 52 HRC has

smallest surface defects of the die are transferred onto the

recently been finished successfully. During the lifetime of

cast component and are unavoidably visible after painting

90000 shots only few very small defects showed up which

or chromium plating. Having tried numerous standardized

could easily be laser-welded.

and special hot-work tool steels the caster could not pro-

Although the caster did not increase the number of shots he

duce more than 3500 shots per die. Using CS1 with 53 HRC

could drastically reduce the maintenance efforts from 780

13000 shots were achieved. Further tests were performed

hours (1.2343) to 290 hours. The improvement of the surface

with a higher hardness of 56 HRC leading to a performance

quality as well as the reduced maintenance work are a clear

of 24000 shots. The increase of the hardness permitted to

technical benefit for the caster.

Fig.6 - Die cast and chromium-plated brake fluid tank of a motorcycle (left), Die cast throttle body (middle) / Die cast case of a memory unit (right) (examples).

The third example concerns memory unit housings, which

trial, the CS1 die with 53 HRC has so far achieved 7100 shots

are more and more installed in modern passenger cars (Fi-

without any problems. The trial is still ongoing.

gure 6 right). They often enclose very sensitive memory or assistance units and have to protect the installed electronic

CONCLUSION

compounds against various impacts. In addition to the chal-

The variety of die-cast components is subject to constant

lenges concerning the high mechanical and thermal as well

changes. The demands on the surface quality and geometri-

as dimensional stability, the cooling fins, which are often

cal accuracy of the cast products are becoming much more

found on cases for electronic purposes, represent a further

stringent for technical and optical reasons. With the tool ste-

challenge for the die. In fact the corresponding grooves in

el CS1, the die casting industry has a new premium hot-wor-

the die are potential starting points of cracks. With the hot-

king steel at its disposal that enables hardness values of up

work tool steel 1.2343, the very high demands on the sealing

to 56 HRC combined with very high toughness. In the range

surfaces lead to tool failure after only 5000 shots. In a recent

of typical working temperatures, CS1 achieves a significantly

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Memorie scientifiche - Pressocolata

higher high-temperature strength and thus greater resistan-

made of CS1, thanks to its significantly higher hardness,

ce to thermal shock cracking. The special transformation

show a noticeable improvement in performance, especially

behaviour of CS1 enables martensitic transformation with

for castings with the highest surface requirements.

great certainty when hardening large dies.

Practical tests carried out by our customers show that dies

REFERENCES [1] [2]

[3]

Spotlightmetal [Internet]. Technologies: Robert Knorre; 2019. Automotive Structural Parts made in HPDC; 2019 Dec 12 [cited 2021 Jan 29]; [1 page]. Availabe from: https://www.spotlightmetal.com/automotive-structural-parts-made-in-hpdc-a-888708/ Information/Age [Internet]. Data&Insight: Aaron Hurst; 2020. Global 5G connections to reach 3.6 billion in 2025 — CCS Insight: 2020 Oct 13 [cites 2021 Feb 08]; [1page]. Available from: https://www.information-age.com/global-5g-connections-reach-3-6-billion2025-ccs-insight-123492091/ Haberling E., Schüler P. Zusammenhang zwischen Vergütungsfestigkeit und Temperaturwechselrissbildung von Warmarbeitsstählen.

Thyssen Edelst. Techn. Ber. 1985 Sep; 11(2):158-161

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Scientific papers - Die casting

AM Process Simulation to Optimise Diecasting Tooling N. Gramegna, D. Boscolo, G. Scarpa, Nardo and F. Bonollo

The innovation of design for diecasting tooling is significantly affected by Additive Manufacturing (AM) technology evolution as well as by the increasing reliability of AM process simulation [3]. The casting process simulation is a well-known standard design procedure to optimize the thermal steady state of each part of the steel die taking into account the limitation of traditional machining process to produce the insert with proper cooling channels [1,2]. The advent of Selective Laser Melting (SLM) or Electron Beam melting (EBM) is opening to free form of cooling channels to control the thermo mechanical behaviour of the steel tooling improving the die life and reducing the risk of local defect in the casting. Further possible development is the application of DED to reparation of the High pressure die casting (HPDC) tooling. The AM simulation tools can simulate different additive processes and various virtual scenarios can be evaluated. The Optimization of diecasting tooling is entering a new era thanks to material, technologies and virtual simulation tool of AM processes.

The study described in this paper is a reference application of HPDC and AM simulation coupling the benefits of the two manufacturing processes. The thermo-mechanical performance of traditional diecasting insert is improved by conformal cooling channels and the cycle time is typically minimized. The SLM simulation validates the 3D printing of steel material taking into account the geometry compensation, the support optimization and the quality of printed part to be treated and machined.

The cost- benefits analysis supports the decision in the design phase validating the optimal geometries for the production of the components, verifying the efficiency of the cooling channels designed to support the quality of the component and the dies life, maximizing the benefits and reducing costs [4].

KEYWORDS: PROCESS SIMULATION, ADDITIVE MANUFACTURING, STEEL INSERT, CONFORMAL COOLING, HIGH PRESSURE DIE CASTING, PROCESS OPTIMIZATION INTRODUCTION High-pressure die casting process (HPDC) is one of the most exploited casting processes. Nowadays the process is used more and more to cast multitude of different sizes and far more complex castings. The principle of the HPDC process is that molten metal (mostly aluminum or zinc) is pressed into the cavity under high pressure. The cavity is filled in a few hundredths of a second. After the melt has solidified, the casting is removed from the open die and afterward the cavity surface is sprayed with a die lubricant water based and blown with air to avoid water stagnation. The die is then

N. Gramegna, D. Boscolo, G. Scarpa Enginsoft Spa, Italy

N. Nardo and F. Bonollo University of Padova, Italy

closed and ready to receive a new portion of molten metal.

The permanent die undergoes severe thermal cycles, since the range of temperatures involved and the little cycle time. Thermoregulation during the heat removal is crucial not only to obtain a good quality part, but it also affects the die life and the production time cycle, cost-effectiveness of

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Memorie scientifiche - Pressocolata the process results strongly dependent onto these factors.

the proposed layouts;

HPDC dies are made of hot working steel, such as H11 and

- Assess techno-economical costs and benefits of a con-

H13. The complex cavity shape is conventionally obtained

formally cooled insert in comparison to a conventional

with machining processes (CNC, drilling, …), thermoregu-

insert;

lation circuits are so restricted to straight line shapes. Thus, meaning that conventional thermoregulation circuits don’t

The expected benefits introducing 3D printed inserts in the

impart optimal thermal (and thermomechanical) behavior,

traditional HPDC tooling are the reduced cycle time (less

especially in case of great complexity of the cavity (such as

solidification time), best casting quality (less defects) and

curved-in shapes, thin thickness inserts, …). The advent of

prolongation of die life (less stressed tooling).

Additive Manufacturing (AM) for metals, and its consolida-

To carry out this analysis in this paper simulation tools will

tion declined in the Powder Bed (and Direct) methods, has

be deployed. In particular thermal behavior of the insert and

paved the way for an innovative way of tooling, opening

part quality will be evaluated through the utilization of MAG-

many possibilities on different levels. The design is freed

MASOFT®, while AM feasibility will be assessed through the

from conventional tooling (machining) constraints, the ma-

Ansys® Print suit.

terial usage is lowered abandoning the subtractive conventional processes, design and different processes and sce-

CONFORMAL COOLING DESIGN

narios can be easily evaluated through increasingly reliable

After the analysis of the conventional design it appeared that

simulation means.

the main issue of the HPDC castings was to be found in lo-

Conformal Cooling technique takes advantage of AM cha-

calized porosity. To solve this issue four inserts where se-

racteristics listed above, die inserts can so be equipped

lected to be candidates, on their own or in different combi-

with free form and small diameter (down to 1.5 mm) cooling

nations, for conformal cooling circuits. The first of this insert

channels, enabling the redesign of the conventional die in-

is an actual separated insert already existing on the slider,

serts, making feasible a much finer control of the thermo-

the other three inserts where derived respectively one from

mechanical behavior of the die. While the literature already

the fixed and two form the ejector die. Due to the narrow

explored and proved the value of applications of AM tooling

dimensions of the spires of the three inserts on ejector and

for injection molding, it appears to be still pretty unexplored

fixed die only one conformal cooling was designed for each,

for HPDC. The aims of this paper are to:

while with a bigger available volume eight alternatives have

- build a DOE Analysis of conformal cooling application to

been designed for the side core insert.

an HPDC die insert to figure out the best alternative among

Fig.1 - Conformal cooling proposed designs.

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Scientific papers - Die casting THERMAL ANALYSIS

rosity, porosity on an evaluation area, FS time and the sum

To evaluate the best alternatives a full factorial DOE was set

of the active circuits. This generated 81 alternative designs,

up based on the created designs. Four factors were defined,

in table 1 the improvements of the DOE winning design in

three factors were set as the three circuits designed for ejec-

comparison to the conventional one; the winning design is

tor and cover die were set to be either active or not, the four-

characterized by 2 conformal cooling circuits: rotating el-

th factor took into account the side core insert, in its eight

lipsoidal circuit for the side core die and the circuit of the

circuit designs plus the possibility of absence of any cooling

ejector die insert 2;

circuit there. Four objectives have been set to minimize: poTab.1 - Achievements of conformal cooling in comparison to the conventional design. Δ% porosity

Δ% Temperature

Δ% cycle time

Δ% productivity

-95%

-77.84%

-16.47%

+19.72%

Conformal Cooling Design

Fig.2 - Critical porosities reduced using conformal cooling.

In addition to these results the die life of the side core insert was evaluated, showing impressive improvement too;

Fig.3 - Die life results improvement: on the left conventional design on the right conformal cooling design, showing a much longer die life duration through the colors on the top of the scale representing the number of cycles.

CFD ANALYSIS

In this specific case, water at 20 ° c with a flow rate of 20 l /

The production process analysis took into account also the

min was the considered medium.

fluid dynamics of the circuits (cfd analysis). Thanks to the

The results show in particular that the thermal delta betwe-

definition of the medium, the medium temperature and the

en input and output does not exceed 5 ° c, indicating a high

flow rate, it is possible to evaluate the efficiency of the circu-

efficiency of both circuits.

its and possible leaks.

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Fig.4 - Conformal cooling cfd analysis: velocity, temperature and HTC results.

AM FEASIBILITY

to calibrate the material and strain scaling factors, therefore

For evaluation of manufacturability through L-PBF process

the results of this analysis give a qualitative idea of the most

of the inserts designed one relevant alternative was selected

critical areas for deformation and stress, more than accu-

to be simulated, the side core insert equipped with the ro-

rate magnitudes of these. The simulation enabled though,

tating ellipsoidal circuit. As already mentioned, the simu-

the construction of a compensated geometry and assessed

lation of AM process will remain on a macroscopic scale.

the feasibility of the channels showing acceptable values of

Exploiting Inherent Strain method, which is based on the

stress and deformation along the conformal channels.

strains evaluation. Lack of resources lead to impossibility

Fig.5 - Conformal cooling cfd analysis: velocity, temperature and HTC results.

Fig.6 - Conformal cooling cfd analysis: velocity, temperature and HTC results.

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Scientific papers - Die casting

COST/IMPACT ANALYSIS

2. AM manufacturability of HPDC die inserts

The cost of a L-PBF produced insert is almost 10 times the

The first point may be considered achieved thanks to two

cost of the same insert produced through conventional to-

aligned results. Firstly, the higher effectiveness of the HPDC

oling due to:

manufacturing process is to be found in the improvement of

- Numerical evaluation Production cost 1.6 times higher

the part quality, assessed by the reduction of the values of

- Energy consumption 1.8 times higher

porosity, hot spot and die soldering effects. Secondly cost

- Powder alloy costs 10 times higher than the same solid

reduction of the process is to be found in the cycle time re-

material

duction, enabling a higher productivity and in the elongation

But the higher production cost is justified by the following

of the die inserts through smaller thermal cycles, lessening

improvements assessed through simulation:

hence the down time for insert substitution.

- the waste castings rate is expected to decrease from a

The second point more specifically deals with the L-PBF

50% to a 10%;

manufacturability, which has been tested in terms of part de-

- the down time for insert substitution considering a pro-

formation and residual stress and strains. The results of the

duction of 1000000 of castings is lessened of the 100%;

set of AM simulations gave the basis to part compensations

- the reduction of the solidification time and therefore

in order to obtain a printed part respecting the demanded

cycle time reduction enables a rise of 19% of the pro-

specifications.

duction rate; CONCLUSIONS AND FUTURE PERSPECTIVES Numerical evaluation of conformal cooling solutions for HPDC die inserts and L-PBF manufacturability of the have drawn an interesting scenario for the future application of these techniques and process in the industry. The most relevant achievements can be divided in two main categories: 1. HPDC process improved cost-effectiveness

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

J. Meckley and R. Edwards, “A Study on the Design and Effectiveness of Conformal Cooling Channels in Rapid Tooling Inserts,” Technol. Interface J., vol. 10, no. 1, pp. 1523–9926, 2009.

H. S. Park and N. H. Pham, “DESIGN OF CONFORMAL COOLING CHANNELS FOR AN AUTOMOTIVE PART,” Int. J. Automot. Technol., vol. 10, no. 1, pp. 87–93, 2009.

Y. Wang, K. M. Yu, C. C. L. Wang, and Y. Zhang, “Automatic design of conformal cooling circuits for rapid tooling,” CAD Comput.

Aided Des., vol. 43, no. 8, pp. 1001–1010, 2011.

K. M. Au, K. M. Yu, and W. K. Chiu, “Visibility-based conformal cooling channel generation for rapid tooling,” CAD Comput. Aided Des., vol. 43, no. 4, pp. 356–373, 2011.

S. A. Jahan, T. Wu, Y. Zhang, J. Zhang, A. Tovar, and H. Elmounayri, “Thermo-mechanical Design Optimization of Conformal Cooling Channels using Design of Experiments Approach,” Procedia Manuf., vol. 10, 2017.

S. Jahan and H. El-Mounayri, “A Thermomechanical Analysis of Conformal Cooling Channels in 3D Printed Plastic Injection Molds,” Appl. Sci., vol. 8, no. 12, p. 2567, 2018.

A. Agazzi, V. Sobotka, R. Legoff, and Y. Jarny, “Optimal cooling design in injection moulding process-A new approach based on morphological surfaces,” Appl. Therm. Eng., vol. 52, no. 1, pp. 170–178, 2013.

Maciej Mazur Martin Leary Matthew McMillan Joe Elambasseril Milan Brandt, “SLM Additive Manufacture of H13 Steel with Conformal Cooling and Lattice structures Nomenclature,” Rapid Prototyp. J., vol. 22, no. 3, 2016.

M. Mazur, P. Brincat, M. Leary, and M. Brandt, “Numerical and experimental evaluation of a conformally cooled H13 steel injection mould manufactured with selective laser melting,” Int. J. Adv. Manuf. Technol., vol. 93, no. 1–4, pp. 881–900, 2017.

A. T. Pradeep, “HPDC Die design for Additive Manufacturing,” 2018.

N. Nardo, “Optimization of a die insert produced through metal powder bed fusion”, 2020, http://tesi.cab.unipd.it/63823/

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Residual stress analysis applied to HPDC alluminium components: a case study E. Fracchia, F. S. Gobber, M. Rosso, Y. Kobayashi, C. Mus

High-Pressure Die Casting (HPDC) is a casting process largely diffused in the aluminium foundries. By HPDC is possible to obtain aluminium castings with thin walls and high specific mechanical properties in short cycle times. Aluminium

HPDC castings are commonly intended for the automotive sector: engine, covers, engine blocks and more in general the powertrain. In recent years, one of the most important focus in the automotive sector is decreasing the powertrain

weight, acting on stock allowances in certain parts of the casting. This reduction can affect the dimensional features and in turn the residual stress inside the casting. Despite that, it is possible to obtain beneficial compression states into the castings by mean of post-process operations, such as shot-blasting, to reduce or remove residual stresses by

mean of heat treatments. Residual stresses can be assessed by an X-Ray residual stress measurement devices, a nondestructive technique that allows observing the process parameters effect into the casting.

In this work, after a detailed analysis of the residual stress measurement available for aluminium castings, a powertrain component realized in aluminium alloy EN AC 46000 was analysed. These analyses involved both dimensional response

and related residual stresses in the as-cast state and the shot-blasted-state on a valve cover, to understand and prevent the residual stress states into the aluminium castings.

KEYWORDS: RESIDUAL STRESS ANALYSIS, ALUMINIUM CASTINGS , HPDC, SHOT-BLASTING, X-RAY METHOD INTRODUCTION Nowadays, the aluminium market grew a lot, mainly thanks to the automotive industries that have invested heavily in both the reduction of fuel consumption and vehicles weight. The interest in aluminium alloys is attributable to their very good mechanical properties, especially if compared to their light-weight (1). In this scenario, aluminium foundries have increased their production a lot, focussing on both reducing cycle times and optimizing casting cooling (2). Particularly, processes such as sand casting (SC), gravity casting (GC), high pressure die casting (HPDC) and low pressure die casting (LPDC) are used to realize aluminium components (3).

High pressure die casting is an automated manufacturing method for casting thin-walled pieces and very complex components, largely used for high production volumes.

This process is characterized by a very high filling-rate of

E. Fracchia

Polytechnic of Turin (DIGEP), ITALY.

F. S. Gobber

Polytechnic of Turin (DISAT), ITALY.

M. Rosso

INSTM c/o Polytechnic of Turin (DISAT), ITALY.

Y. Kobayashi

SURFACETEC COMPANY Development Group, JAPAN.

C. Mus

Endurance Overseas, Chivasso, Turin, ITALY.

the die by the molten aluminium that solidifies under high pressure. Cycle times may change dependently on the dimensions of the pieces but are usually relatively short.

This production process can lead to residual stresses into

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Scientific papers - Die casting

the casted parts, like any other manufacturing process.

MATERIALS AND EXPERIMENTAL METHODS

Residual stresses are self-balancing tensile or compressive

The investigated powertrain components were realized

stresses existing into the material independently from the

in aluminium alloy EN46000 by high pressure die casting.

presence of an external load. The causes that give rise to

The campaigns of residual stress measurements were

residual stresses are uneven plastic deformations, surface

conducted on the components showed in Fig. 1. For all

modifications and thermal gradients (4). These stresses are

investigated parts, the same HPDC process was carried

generally classified according to the quantity of material

out: (i) die lubrication; (ii) metal injection, (iii) solidification,

involved (5). Type-I-stresses are macro residual stresses

(iv) extraction, (v) water quenching, (vi) trimming, (vii)

involving millimetres of material and are typically caused

shot blasting. Particularly, the last process step has been

by manufacturing processes. Type-II-stresses are micro-

identified as the most significative to be investigated.

residual stresses involving micrometers of material while

X-ray analysis was performed on selected components

type-III-stresses occur at the atomic scale. The proper

by the portable X-ray Residual Stress Analyzer μ-X360s,

choice of the measurement method makes it possible to

equipped with Cr X-ray target. The measurement is

asses all types of residual stresses (4). Utilizing neutron

carried out by comparing the lattice parameters of the

diffraction (6), the penetration in aluminium is about 50

sample to the theoretical values of the unstressed lattice

mm (7,8). Synchrotron x-ray (9) ensures penetration in

for the same material, using the cosα method. The

aluminium of about 100 mm. Relaxation measurements

diffractometer analyses the 2θ-shift of specific diffraction

are based on the residual stresses release during the

peaks collecting data on a 2D detector (13) and the residual

processing of the material (10). This method leads to

stress measurement is made by using a collimated X-ray

reach 10μm-10cm by hole drilling and 10cm-1m in deep

incident beam as a probe directed to the sample surface

hole drilling. The magnetic method is only suitable for

with a specific exposure angle for a determined time. An

ferromagnetic materials (11) and ensures penetrations of

integrated LED marker and a CCD camera make the sample

10μm-1mm;

positioning easier. Measurements may be carried out along

the ultrasonic method guarantee penetrations of about

two different crystal planes, [311] and [222], each crystal

150mm while thermoelastic and photoelastic methods

plane requiring different parameters (i.e. detector-sample

10μm-1mm. Utilizing the evaluations of the materials’

distance, detector-sample angle). The measurement

hardness (12) is possible to assess the residual stress

of residual stress on plane [311] is made by adopting a

in the first 10μm-1mm of the material and, finally, by

25° detector inclination and a 39 mm distance from the

means of X-ray Diffraction, the penetration is of about

sample surface, while for plane [222], 35° and 25 mm are

tens of micrometers, raising up to 1mm by adopting

chosen. The aim of the analysis was the comparison of the

electropolishing techniques for removing the uppermost

stress state in different components as a function of two

layers of material. In this work, the x-ray diffraction method

parameters: shot-blasting and lighter design. The main

was adopted in aluminium valve covers for automotive

parameters affecting the residual stresses in powertrain

usage, obtained by HPDC technique, with the aim to :

components are the wall thickness, that influences the

• assess the applicability of this non destructive method

solidification rate, and the shot blasting, that affects the

to complex geometries;

surface tension state. The points selected for the analysis

• evaluate the impact of design and manufacturing

were chosen after performing optical scan analysis and

process change on residual stresses;

FEM simulations, to highlight the possible critical points

• assess the possibility to consider the technology

in terms of residual stresses involved. After performing

suitable for in-process qu

the first residual stress measurements in the as-cast state,

ality control.

the covers were shot blasted and then subjected to the second residual stress measure.

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Memorie scientifiche - Pressocolata

Thin large valve cover

Massive valve cover

Fig.1 - Components realised, tested and measured (images not to scale each other).

As thin large valve covers regard, one cover was analysed

before and after shot blasting: Cover 1 (as-cast) and Cover

1S (cover 1 after shot blasting). The cover was tested only in [311] configuration because of the high numbers of points selected. Massive valve covers analysed were two,

and were named after : Cover Basic (as-cast), Cover Evo (as-cast) and Cover EvoS (cover Evo after shot blasting). It is important to note that Evo weights 5% in less than Basic

because Cover Basic presents different wall thickness to Cover Evo: Basic wall thickness is 4.5 mm, Evo wall

effect of the shot blasting, that change the tensional state

of the point from tensile to compressive state. Moreover,

it is also clear that all parts of the cover benefit from the shot blasting, as highlighted for sample Cover 1S in both

the line chart and the Debye ring. If the previous stress state is in tensile condition (point 24) or a quasi-tensile

condition (as points 1, 12, 17), the shot blasting causes

a strong impact on the residual stress changing it into a strong-compressive state.

thickness is 2.5 mm. Details about the lighter design are showed in Fig.2-c and d.

RESULTS AND DISCUSSION Thin large valve cover

One thin large cover was analysed in the as-cast and

trimmed state and then after shot blasting. Twenty-four

possible critical points were selected where residual stress were measured (as illustrated in Fig.2-a).

Fig.3 shown some details about the measurements.

Camera image depicts the analysed point. The red-LED

marker visible in the figure indicates the analysed point, that must be located as much as possible into the middle

of the rectangular-shaped dotted yellow-lines. The

Debye ring indicates the residual stress state. As clearly

noticeable from Fig.3-a, Debye ring in shot-blasted covers have smoothed edges suggesting a homogeneous stress state. Fig.3-b displayed the line chart for analysis performed on planes [311]. For points 13, 14 and 22 it was

not possible to perform measurements in planes [311] because of the shape of the cover.

As point 24 regards, it becomes evident the beneficial

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Scientific papers - Die casting

Fig.2 - a. Optical analysis in thin cover in as-cast (left) and shot blasted (right) states and analysed points; b. analysed points in massive valve cover; c. Lighter design in massive cover; d. Wall thickness in the massive cover.

Fig.3 - a. Results obtained for ‘thin large valve cover’ in the as-cast state (Cover 1) and after shot blasting (Cover 1S). Upper images: points #9 and #24: Debye rings and camera images of the referred points. b. line chart of measurements performed.

The shot blasting influences the residual stresses

equalizing it along the entire surface. In the as-cast cover, the average tensional stresses values based on all points analysed was -50±36.6 MPa, while after shot blasting the

average was -104.6±13.1 MPa. The high standard deviation

in the as-cast state was motivated by the strong variations

in the measured points: from +36 MPa (point 24) to -130 MPa (point 20).

MASSIVE VALVE COVER

For these covers the wall thickness reduction contributes to weight saving and has an impact on the residual stress

state. In Fig.4 residual stresses are shown for both [311]

La Metallurgia Italiana - November/December 2021

and [222] planes. From the measurements, a compressive

state on the surface of Cover-Basic arises, with an average

value of almost -50 MPa on [311] planes and -60 MPa on [222] planes. On the other hand, the lightened cover Evo

results in a tensile or quasi-tensile state in some parts

of the cover surface, with average values of -5 MPa in [311] and -35 MPa on [222]. The lateral points (7 and 8)

showed similar tensional state for both Cover Basic and Cover Evo and in both planes. After the shot blasting, a

general compressive residual stress results on the surface of Cover Evo S, with average values of almost -100 MPa along [311] planes and -115 MPa on [222] planes.

Further considerations can be done: first of all, the

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lightened cover (Evo) results in higher distortions and a

light compressive state. Secondly, as attended, the shot

blasting caused an increase in the compressive state, without residual tensile stress. From Fig.4 resulted that

points 5 and 6 were not measurable in planes [311] because

the cover shape makes impossible the approaching of the instrument at the correct distance, while in Cover Evo S

on [222] planes, measurements for points 5 and 6 were not shown because of the strong distortions detected and/or the high standard deviations. The weight reduction affects the tensional state increasing the possibility of having

tensile stresses or slight compressive stresses. In this

respect, weight reduction caused the change from the

average value of -45±28.5 MPa in Basic cover to -27±48.3 MPa in Evo cover on planes [311], and from -64.4±23.8

MPa to -47.3±29 MPa on planes [222]. The high standard deviation is motivated by the uneven tension state, typical for the as-cast products. On [311] planes maximum value

was +49 MPa and minimum value -75 MPa, on [222] planes the maximum value was -8 MPa and minimum value -101

MPa. Since the lighter cover Evo presents tensile stress

in point 1, the cover was further investigated in the shot blasted state founding the average values of -100.2±11.5 MPa on [311] and -120.7±15.4 MPa on [222].

Fig.4 -Line charts for Cover Basic and Cover Evo.

CONCLUSIONS In

this

work,

two

powertrain

components

were

investigated in terms of residual stresses, in the as-cast

and trimmed state and after shot blasting. Referring to the aims of the activity , the main conclusions follow.

1. The X-ray diffraction method (non destructive) can be applied, with some limitation in accessibility to certain area, to complex geometries.

2. The casting geometry (wall thickness) affects residual

stresses. Components investigated, reported in Fig.1, are

the thin large valve cover and the massive valve cover.

Particularly, massive valve cover was investigated in the

Basic shape and in the Evo shape, to highlight the effect of

the weight reduction on the tensional state. In fact, despite the weight reduction appears as very important for both

the fuel consumption reductions and the cost savings, it influences the residual stresses too. As the thin large

valve regards, analysis highlight the beneficial effects of the shot blasting that has harmonized the tensional state

La Metallurgia Italiana - Novembre/Dicembre 2021

from the average value of -50.2 ± 36.6 MPa to -104.6 ± 13.1 MPa. Measurements were performed only on planes

[311]. In the massive large cover, the analysis performed

on Cover_Basic evidenced a compressive state on the cover surface. Furthermore, maximum and minimum

values measured in Cover_Basic are -27 MPa and -99 MPa on planes [311] and -26 MPa and -92 MPa on planes

[222]. The weight reduction obtained by the thinning of

the cover wall, as indicated in Fig.2, caused in Cover_Evo a variation in the tensional state. In this sense, on Cover Evo were documented stresses maximum and minimum respectively of +49 MPa and -75 MPa on [311] planes and

of -8 MPa and -101 MPa on planes [222]. From these values appears quite evident the presence of an uneven tensional state more pronounced that in Cover Basic.

3. Manufacturing process steps ( i.e. shot blasting) affect residual stresses. After the shot blasting, the cover presents a different tensional state, with a homogeneous

compressive state having -88 MPa as maximum and -117

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Scientific papers - Die casting

MPa as a minimum compressive state on [311] planes and -103 MPa and -143 MPa on [222] planes. These results

evidenced the effectiveness of the residual stresses

measurements, that underlined the impact of the lighter

design on the tensional state in castings. Furthermore, the shot blasting process brings uniformity in the tensional

state improving the quality of the powertrain components,

reducing the possibilities to triggering into fractures during the assembling of the engine components.

4. The X-ray diffraction (non destructive) technology is suitable for in-process quality control to be adopted during new products development phase. In particular portable X-ray measurement to evaluate the residual

stresses in the casting parts is a very interesting source for quickly evaluating both the residual stresses due

to casting process and the beneficial effect of the shot

blasting, allowing the analysis of various shapes of the castings.

AKNOWLEGMENTS

The activities described have been undertaken within the ICARO- Project codes: 309/2 and 309/3, in the

frame of “IR2” Industrialization of Research Results within the Regional Operational Programme “Regional

Competitiveness and Employment”.(E.R.D.F. 2014/2020

Action I.1b.1.1. – “Support for the economic exploitation of innovation through experimentation and the adoption

of innovative solutions in processes, products and

organisational formulas, as well as through the financing of the industrialisation of research results”) – Legal basis: EU Regulation n. 651/2014.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

Fracchia E, Gobber FS, Rosso M, Actis Grande M, Bidulská J, Bidulský R. Junction characterization in a functionally graded aluminum part. Materials (Basel). 2019;12(21):3475.

Lombardo S, Fracchia E, Gobber F, Rosso M. Gestione delle conchiglie nella colata in gravità e possibili vie per migliorarne prestazioni e durata. La Metallurgia Italiana. 2019; 6.

Otarawanna S, Dahle AK. Casting of aluminium alloys. In: Fundamentals of Aluminium Metallurgy: Production, Processing and Applications [Internet]. Woodhead Publishing Limited; 2011; 141–54. Available from: http://dx.doi.org/10.1533/9780857090256.1.141.

Schajer G S, Ruud C O. Wiley. Practical Residual Stress Measurement Methods. 2013.

Kandil FA, Lord D, Fry T. National Physical Laboratory. A review of residual stress measurement methods: a guide to technical selection.

NPL Mater Cent. 2001;1–42.

Ripley MI. Residual stress measurement using neutrons. Mater Forum. 2006;30:219–24.

Fitzpatrick ME; Fry AT; Holdway P; Kandil FA; Shackleton J; Suominen L. Determination of residual stresses by X-ray diffraction.

Measurement Good Practice Guide No 52; 2005; Available from: http://eprintspublications.npl.co.uk/2391/.

Guo J, Fu H, Pan B, Kang R. Recent progress of residual stress measurement methods: A review. Chinese J Aeronaut. 2019; Available from: https://doi.org/10.1016/j.cja.2019.10.010.

Tsakalakos T, Croft MC, Jisrawi NM, Holtz RL, Zhong Z. Measurement of residual stress distributions by energy dispersive X-ray diffraction synchrotron radiation. Proc Int Offshore Polar Eng Conf. 2006;57–64.

Schajer GS. Relaxation Methods for Measuring Residual Stresses: Techniques and Opportunities. Exp Mech. 2010;50(8):1117–27.

Gur H. Review of Residual Stress Measurement by Magnetic Barkhausen Noise Technique. Mater Perform Charact. 2018.

Hosseinzadeh AR, Mahmoudi AH. An approach for Knoop and Vickers indentations to measure equi-biaxial residual stresses and material properties: A comprehensive comparison. Mech Mater [Internet]. 2019;134:153–64.

Sasaki T, Kobayashi Y. X-ray multiaxial stress analysis using two Debye rings. Adv X-ray Anal. 2009.

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Evaluation of fracture toughness in HPDC aluminium alloys to estimate crashworthiness in automotive parts I. Tarhouni, D. Frómeta, A. Lara, S. Parareda, M. da Silva, D. Casellas, S. Wiesner

Aluminum high pressure die casting (HPDC) alloys are widely applied in the automotive sector. The constant needs for

lightweight materials open a new opportunity for Al castings in structural applications in vehicles. New HPDC Al alloys

with high ductility are available and are potential candidates for Body-in-White applications with crash requirements.

Therefore, an assessment of the crashworthiness of these materials is required. In previous publications, the authors

demonstrated that the fracture toughness, measured in the frame of fracture mechanics can be related to crash resistance in high strength steels and aluminum sheets. In this context, the characterization of the fracture toughness

of two aluminum alloys with different ductility (AlMg4Fe2, AlMg4Fe2Zn3) was assessed following linear elastic fracture mechanics (LEFM), in terms of 𝐾 𝐼𝑐 and elastic-plastic fracture mechanics (EPFM), in terms of the essential work of fracture, 𝑤𝑒. The results show that LEFM is not suitable to evaluate the fracture toughness of HPDC alloys with a

significant amount of plasticity. On the other hand, it is showed that 𝑤𝑒 describes the fracture toughness for high ductility alloys and it is here proposed as a material property to predict the crashworthiness of ductile HPDC alloys.

KEYWORDS: ALUMINUM, HIGH PRESSURE DIE CASTING, CRASHWORTHINESS, FRACTURE TOUGHNESS, EWF INTRODUCTION The electrification of cars, and the control on the CO2 emission and fuel consumption are pushing automakers toward adopting lighter structures. New materials and forming processes have been developed in the last years to meet these demands, as advanced high strength steels (AHSS) and high strength aluminum alloys [1]. Aluminum high pressure die casting (HPDC) alloys are widely applied in the automotive sector. Their ability to create lightweight parts without sacrificing the strength, and their distinctive features such as corrosion resistance, excellent electrical conductivity and high stability for complex shapes make them good candidates for powertrain parts, bodyin white and chassis. Recent developments in HPDC have provided new opportunities for structural parts in electrical vehicles [2, 3, 4]. However, their efficient implementation depends on the ability of the car industry

Ilef Tarhouni, David Frómeta,

Antoni Lara, Sergi Parareda, Manel da Silva Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Spain

Daniel Casellas

Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Spain - Division of Solid Mechanics, Luleå University of Technology, Sweden

Stuart Wiesner

Rheinfelden alloys, Germany

to optimize the fatigue and fracture performance.

Crashworthiness is one of the relevant material properties for lightweight construction of structural automotive parts. However, it is a complex property to measure. It

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Scientific papers - Die casting is usually measured with expensive and time-consuming

this need, the essential work of fracture approach was

tests, which often do not inform about the intrinsic

introduced in the frame of EPFM to determine the fracture

material resistance to crash. Thus, Al manufacturers and

toughness for ductile metal sheets under plane stress

carmakers are constantly looking for laboratory scale

state [9,10].

tests to characterize the crash behaviour and the fracture resistance. The work of Frómeta et al. showed that

This paper aims to assess the evaluation of fracture

tensile properties such as the fracture elongation or the

toughness of two HPDC aluminium alloys with different

energy under load-displacement curve failed to provide

ductility range, with the objective to define the best

a good characterization of the crashworthiness of AHSS

approach to estimate crashworthiness at lab scale. Two

[5]. Alternatively, some works in AHSS pointed that the

fracture toughness approaches based on LEFM (𝐾𝑐) and

fracture toughness, measured within the framework of fracture mechanics, is the relevant material property to

EPFM (𝑤 𝑒) were presented and discussed.

describe the fracture resistance in crack related processes, like edge-cracking and crash tests [6,7]. More recently the

THEORETICAL PRINCIPALS

work of Pujante et al. also showed that fracture toughness

LINEAR ELASTIC FRACTURE MECHANICS, 𝐾𝐼𝑐

could be used to rank crashworthiness in high strength Al sheets [8]. Thus, fracture toughness emerges as a relevant material property to estimate crash resistance.

The plane strain fracture toughness, 𝐾 𝐼𝑐, is the crack-

extension resistance under mode I and linear-elastic conditions at the onset of 2% of the crack extension. The

The fracture toughness evaluation of thin parts, as thin

test procedures to measure it is defined in ASTM-E399

sheets used in chassis and Body-in-White parts or thin-

standard. The method involves testing fatigue pre-

walled components obtained by HPDC, is experimentally

cracked notched specimen. The most used specimens are

challenging, because fracture toughness is thickness

C(T) and SE(B). The load-displacement curve is recorded

dependent. Specimen thickness defines if plain strain

during the test. 𝑃𝑄 corresponds to 2% apparent increment

or plain stress fracture conditions prevail. Most of the

of crack extension and established by a 0.95 deviation

standardized tests are defined for thick specimens, under

from the linear portion of the recorded curve as indicated

plane strain condition. In addition, the lack of experimental

in Fig.1. From the 𝑃 𝑄 value and the measured crack length

standards to evaluate the fracture toughness when the thickness requirement is not fulfilled hinders the proper knowledge of their fracture resistance. In response to

for each test, the conditional fracture toughness 𝐾 𝑄 is

calculated using the equation:

Eq (1)

Fig.1 - 𝑃𝑄 determination as described in ASTM-E399.

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Memorie scientifiche - Pressocolata where a is the crack length, t 0 is the sheet thickness, W is the

specimen width and b is the half of specimen width. Since 𝐾 𝐼𝑐 is thickness dependent i.e., toughness decreases with

increasing the specimen size until reaching a plane strain

mode, the following validity requirements are imposed to ensure that the measured 𝐾𝐼𝑐 is thickness independent.

Eq (2)

Eq (3)

where σ ys is the 0.2 % offset yield strength and P max is the

that the work performed at the crack region of a ductile

maximum load recorded during the test. The second

material fractured under elastic-plastic condition and

requirement, Eq (3) is to ensure that the non-linearity

plane stress state (w f) is proportional to the ligament

observed corresponds to the crack initiation and not to

length (𝑙 0) and can be separated into two parts: (i) the

essential work of fracture performed in the inner fracture

large plastic zone in the ligament [9].

ELASTIC-PLASTIC FRACTURE MECHANICS, 𝑤𝑒

The essential work of fracture (EWF) concept proposes

process zone (𝑤 𝑒) and (ii) the non-essential work of

fracture performed in the outer fracture process zone (w p) [6]. The total work of fracture (wf) can be written then as: Eq (4)

where 𝛽 is a constant, which depends on the shape of the

two notches is fully yielded prior to crack initiation and

plastic region. Thus, by testing a series of geometrically

the plastic zone is uncontained within the ligament Fig.2.

similar specimens, the separation of the two energies is

The test is usually performed on double edge notched

possible. Eq (4) is valid only if the ligament between the

(DENT) specimens.

(a)

(b)

Fig.2 - (a) DENT specimen ;(b) Linear relationship between total specific work and the ligament length and determination of 𝑤𝑒 at the y-axis intercept.

MATERIALS

(Castaduct-18) alloys. The chemical composition and the

Two high performance HPDC Al alloys were used in

tensile properties are listed in tables 1 and 2.

this study: AlMg4Fe2 (Castaduct-42) and AlMg4Zn3Fe2

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Scientific papers - Die casting

Tab.1 - Chemical composition (wt%) of Castaduct-42 and Castaduct-18. The balance in Al. Alloy

Si Min.

Castaduct-42

Max.

0.2

Min.

Castaduct-18

Max.

0.2

Fe

Mg

1.5

4.1

1.7

4.5

1.5

4.1

1.7

4.5

Cu

Mn

Zn

Ti

0.2

0.15

0.3

0.2

3.3 0.2

0.15

3.6

0.2

Tab.2 - Tensile properties of Castaduct-42 and Castaduct-18.

Alloy

Yield strength [MPa]

Tensile strength [MPa]

Total Elongation [%]

Castaduct-42

121

259

19.4

Castaduct-18

187

311

6.9

METHODS

analysis was performed in the elastic regime and several

DENT specimens of 120 x 60 x 3 mm (H x W x T) were used

contours were employed around the crack tip to calculate

for the LEFM tests. The edge notches were machined

the energy release rate.

by electrical discharge machining (EDM) then followed by a fatigue pre-crack of 1.5mm. The ligament length is

RESULTS AND DISCUSSION

about 14 mm (a/b=0.8) as indicated in Fig.3. The test was

EXPERIMENTAL RESULTS

performed at a quasi-static strain rate of 1 mm/min with a

Values of 13 MPam1/2 and 18 MPam 1/2 were calculated

gauge length of 25mm.

for Castaduct-42 and Castaduct-18 respectively (Fig.3).

The validity requirements were then checked for both

The EWF experimental test was carried out on a batch of

alloys. The Castaduct-18 fulfilled the first requirement

specimens with a ligament length varying between 6 and

as (Pmax/PQ=1.1). On the other hand, the ratio exceeded

14 mm, 2 samples were used for each ligament length. The

1.1 for the Castaduct-42 (Pmax/PQ=1.3). Consequently, 𝐾𝑄

test conditions, fatigue pre-crack and gauge length were the same as for LEFM tests. The values of w f were obtained

is meaningless and not giving a toughness value for the Castaduct-42. LEFM is then applicable only in the case

by integrating the area under the load displacement curve

of Castaduct-18. EPFM should be assumed in the more

and dividing by the cross-section area. 𝑤𝑒 was determined

ductile alloy. To verify if 𝐾𝑄 is equivalent to 𝐾𝐼𝑐 in the case

detailed in previous works [4,5,7].

for this alloy, much higher than the thickness of the

The simulation of the experimental test has been made

specimens (3 mm). Therefore, 𝐾𝑄 cannot be considered

from the extrapolation of wf vs l0 data to zero ligament

length. Details about the experimental procedure are

by finite element (FE) code” ABAQUS”. Due to the symmetry in the geometry and loading condition, only

of Castaduct-18, the specimen size requirement must be

met. A value of 25.8 mm of thickness should be satisfied

as 𝐾 𝐼𝑐 , then it is the fracture toughness for the tested thickness.

1/8 th of the geometry has been modeled. To reproduce the real behavior of the material, the true stress-strain curve obtained from a tensile test was introduced in the model. A 3D eight-nodes element was used for the FE calculation. For the crack tip, singular elements were used and a finer mesh to improve the accuracy. The

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Fig.3 - 𝑃 𝑄 determination from load-displacement curves of Castaduct-18 and Castaduct-42.

Typical load-displacement curves of the DENT specimens

energy separation given by the EWF protocol are valid.

obtained from the EWF experiments are shown in Fig.4. It

The measured toughness in terms of 𝑤𝑒,is 36 kJ/m2.

can be observed that the curves are self-similar for both alloys. The Castaduct-42 showed a larger area under the load displacement curve compared to Castaduct-18,

However, 𝑤𝑓 does not change for different specimens in Castaduct-18, which means that the EWF approach is not valid for the case of Castaduct-18 alloy.

which is consistent with their higher ductility. On the

Digital Image Correlation (DIC) technique was used to

other hand, the Castaduct-18 reached higher maximum

examine the evolution of the plastic zone in the ligament

load. The sharp drop after the maximum load indicates a

zone during the fracture process. DIC results confirmed

more brittle fracture behaviour, which is also consistent

that the complete yielding condition, necessary for the

with their low ductility.

validity of the EWF method, was extensive and proceeded

Fig.4 shows the evolution of 𝑤 𝑓 vs 𝑙0 for both alloys.

the crack initiation in the case of Castaduct-42 but fails

It is observed that 𝑤 𝑓 linearly scales with 𝑙 0 in the case

of Castaduct-42, which indicates that the premises of

for Castaduct-18. Thus, EPFM does not describe the behaviour of low ductility alloys.

Fig.4 - Load-displacement curves and EWF for Castaduct-18 and Castaduct-42.

Fig.5 - DIC measurements of the plastic zone ahead of the crack tip for the two studied alloys.

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Scientific papers - Die casting

NUMERICAL RESULTS

Several contours were used for the calculation of KI. It can

Since the conditional toughness 𝐾𝑄 is meaningless for

be seen from table.3 that the last several contours give

independent results. The K I extracted from the FE model

Castaduct-42 alloy, only Castaduct-18 is modelled. The Von Mises stress distribution is shown in Fig.6. The low

agrees well with the value obtained in experimental LEFM

degree of plasticity in the ligament zone can be seeing.

tests (table 4).

Fig.6 - Von Mises stress distribution at the crack tip.

Tab.3 - Stress intensity factor in mode I (KI) extracted form FE modelling at different contours.

KI [MPa.mm 1/2] Castaduct-18 Position Middle of the crack font

contour 1

contour 2

contour 3

contour 4

contour 5

contour 6

606.7

629.8

632.4

633.1

633.3

632.7

Tab.4 - Comparison between experimental and FE modelling results.

Experimental (MPa.m1/2)

Numerical (MPa.m1/2)

18

20

Castaduct-18

SUMMARY AND CONCLUSIONS

fracture toughness. It is proposed as a testing method

• The development of a significant amount of plasticity

to estimate crashworthiness for HPDC alloys with high

at the crack tip in the case of the ductile HPDC alloy

ductility.

(Castaduct-42) restrained the use of LEFM. Thus, EPFM

• The numerical verification of the path independence

method should be used for high ductility alloys.

exhibits results that confirm the robustness of the

• LEFM can be applied to low ductility HPDC alloy

implementation of LEFM toughness.

(Castaduct-18).

• The characterization of fracture resistance of the HPDC

ACKNOWLEDGEMENTS

Al alloys developed for crash applications must be

This work was financially supported by the Catalan

done in the frame of EPFM. In this sense, the Essential

Government through the funding grant ACCIÓ-Eurecat

Work of Fracture methodology gives reliable values of

(Project Optilightmat-2020).

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Scientific papers - Die casting

Temperature and microstructural condition dependence for thermal diffusivity and thermal condutivity of a casting Al-Si-Cu-Mg alloy E. Gariboldi, C. Confalonieri, R. Wang, M.C. Poletti, B. Stauder, R. Fernández Gutiérrez

Thermal and electrical properties as well as mechanical properties of age-hardenable Al alloys are affected, both at room and at high temperature, by their microstructural condition. This behaviour has to be considered not only for wrought but also for casting alloys, such as for the Al-7Si-0.5Cu-0.4Mg, characterized by multiple precipitation sequences investigated in the paper. In these conditions the temperature dependence of thermophysical properties, generally obtained performing tests during isochronal heating, is not only related to the initial microstructural condition, but also to heating rate, a test parameter whose range is often limited by testing methodologies and equipments. These effects have to be taken into account in cases where a multipurpose material characterization or a comparative analysis of result is intended to interpret microstructural changes. Ex-situ tests can help the separation of microstructural changes effect from temperature-related ones. Examples of the combined techniques and analyses are illustrated.

KEYWORDS: Al-7Si-0.5Cu-0.4Mg, TEMPERATURE-DEPENDENCE, THERMAL DIFFUSIVITY, ELECTRICAL CONDUCTIVITY, DILATOMETRY INTRODUCTION Among the widely applied Al-Si-Mg alloys, the simple addition of Cu demonstrated to beneficially improve the high temperature performance [1, 2], so that temperature and stress/strain cycles can be withstood by complex-geometry components without the addition of exotic elements.

When these alloys, with excess Si and Cu-containing, are solution treated and artificially aged, secondary Si intragranular particles adds up to the metastable phases of β-Mg2Si

precipitation sequence [3] and to phases of the quaternary Q-phase one [4]. The relatively high dissolution temperatures and slow coarsening kinetics of these phases lead to increase both temperature and time at which particle strengthening occurs with respect to Al-Si-Mg alloys.

As for other age-hardening alloys intended to be artificial-

E. Gariboldi, C. Confalonieri

Politecnico di Milano, Dipartimento di Meccanica (Italy)

R. Wang, M.C. Poletti

TU Graz, Christian Doppler Lab. for Design of high-performance alloys by thermomechanical processing, TU Graz (Austria)

B. Stauder, R. Fernández Gutiérrez Nemak Linz GmbH, Linz (Austria)

ly aged (AA) or serviced at relatively high temperature, the following points should be considered: i) local cooling rate following a solution heat treatment (SHT) affect precipitate evolution during aging/service, both in terms of precipitate, volume fraction, nucleation sites and kinetics; ii) secondary phases affect not only strength, but also on the change of volume of the alloy, iii) secondary phase-related effects La Metallurgia Italiana - November/December 2021

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can be observed also for thermal or electrical properties. In

specific properties. Multiple characterization techniques

parts of complex geometry and service conditions, the in-

and heating rates can be successfully used to improve the

teraction between all these features is not easy to foreseen

interpretation of microstructural changes, well exemplified

and good understanding of separate effects should be con-

in [7]. Whenever the multipurpose material characterization

sidered.

could include only a limited set of tests, or lab equipment

Focusing on point (i), the effect of SHT and of its final co-

has different operating ranges, the set-up of experiments

oling on further precipitation during aging treatments at

should be taken into account. The possibility to split micro-

180-230°C of Al-7Si-0.5Cu-0.4Mg alloy with homogene-

structural condition from test temperature effects, and of

ous solidification structures was shown to be negligible

excluding this latter could also be helpful for these analyses.

for SHT cooling rates exceeding 10-20 K/s by Ram et al [6]

A comparative analysis of characterization methods is here

and will be not investigated in the present paper. Concer-

proposed for Al-7Si-0.5Cu-0.4Mg where multiple precipita-

ning points (ii) and (iii), the temperature-dependence of

tion sequences of low amount of secondary phases occur.

age-hardening alloys can significantly differ from that of

This paper shows the effects induced by initial temper and

commercially pure Al, with thermophysical properties both

testing conditions on in-situ dimensional stability and ther-

to initial microstructure and heating rate in the widely adop-

mal diffusivity, and ex-situ electrical conductivity.

ted isochronal-type tests, where adopted heating rates are related to test methodology and equipment used to obtain

MATERIALS AND EXPERIMENTALS

Tab.1 - Chemical composition of the investigated alloy (mass %).

Si

Cu

Mg

Fe

Mn

Ti

Al

6.83

0.531

0.379

0.107

0.073

0.12

Bal.

The investigated material was an Al-7Si-Mg-Cu alloy (actual

Ex-situ indirect electrical conductivity measurements at

chemical composition given in Table 1). Cylinder heads par-

20°C were performed by eddy current with frequency 60

ts were cast by the Rotacast®-method, where the crucible

kHz with an 8 mm diameter probe. Sets of 5 measuremen-

and attached mould slowly rotate around a defined horizon-

ts were performed on water cooled samples extracted from

tal axis, allowing the liquid metal to progressive and regu-

a ventilated oven following set thermal cycles. Specifically,

larly fill the mould. 15X15 mm2 section bars were machined

these ex-situ tests were performed at different times during

from as cast parts in regions where SDAS was close to 32 µm

the heat treatment of SHT+AA4h sample to check the sen-

[6]. Cylindric samples for dilatometric tests (5 mm diameter,

sitivity of the method to microstructural changes. Later, the

20 mm length) and discoidal samples (12.7 mm, 2 mm thi-

tests were performed on AC, SHT, SHT+AA4h samples, du-

ckness) for thermal diffusivity and eddy current tests were

ring isochronally furnace heating from 20 to 530°C at 1°C/

machined from these bars.

min and 10°C/min rates, corresponding to those adopted in

In order to test the alloy in different temper conditions, in

thermal diffusivity and dilatometric tests.

addition to the samples in the as-cast (AC) condition (tested

Thermal diffusivity of samples in the three alloy conditions

some months after casting), other sets of samples were so-

were performed by means of Laser Flash Analyzer during

lution heat treated (SHT) at 530°C for 4.5 h and quenched in

heat cycles 20-530-20°C in vacuum with an average heating

water at about 15°C/s. Some specimens were tested imme-

rate of 1°C/min (0.6-2°C/min actual range).

diately after SHT or stored at -18°C before testing. (SHT+A-

Dilatometric tests on different initial conditions have been

A4h) condition was obtained after SHT followed by, artificial

performed on a vertical dilatometer equipped with quartz

aging at 230°C for 4h to obtain an overaged [6], but rather

rod, with 20-530-20°C heating/cooling cycles at 10 and 1°C/

microstructurally, mechanically and dimensionally stable

min.

condition.

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Scientific papers - Die casting

RESULTS AND DISCUSSION

second phases progressively depletes the matrix of solute

Electrical conductivity

elements, thus increasing its electrical conductivity. It can

The room temperature electrical conductivity of a single

be worth mentioning that at this aging temperature the al-

specimen at different times of the heat treatment cycle is

loy reaches peak hardness in about 1 hour [2], after which

correlated to the microstructural condition, as shown in

electrical conductivity still increases.

Figure 1-left, where the temperature profile of the heat tre-

The results of isochronal ex-situ electrical conductivity te-

atment is plotted in blue color. Figure 1 presents the avera-

sts on AC, SHT, and SHT+4hAA samples are shown in Figu-

ge of the 5 measurements; standard deviation data are not

re 1-rigth. The general trend can still be explained in terms

shown, and they range between 0.01 and 0.025 MS/m de-

of solid solution content (mainly of Mg and Si). First, above

pending on the material condition. During the first isother-

200°C precipitates form in SHT sample, while they increa-

mal treatment, the initial high electrical conductivity of the

se in AC sample and, in a less extent, in overaged sample.

AC sample decreased within the first few minutes spent at

Then, the conductivity starts to decrease due to solid solu-

530°C to an almost constant value. The following isothermal

tion above about 350°C,

aging treatment at 230°C brought a progressive increase of

converging to the same value for all the samples, since the

the electrical conductivity that is still increasing after 4h hol-

final microstructural condition is the same. The

ding. This behaviour can be correlated to the amount of ele-

increase of electrical conductivity occurs more rapidly and

ments remaining in solid solution in the α -phase at different

at lower temperatures for low temperature rates.

time. This simplified explanation further neglects the effects

Only above about 450°C, the differences between different

different solute elements and of the presence of secondary

heating rates and initial material conditions reduce.

phases. At the high SHT temperature, elements rapidly dif-

In the SHT sample, the increment of the conductivity is hi-

fuse and with high solubility, such as Mg and Si, rapidly enter

gher than in AC and SHT conditions due to the highest chan-

in solid solution causing a rapid decrease of electrical con-

ge in element solubility.

ductivity. During the artificial aging stage, the formation of

Fig.1 - Results of ex-situ electrical conductivity tests performed at room temperature during two-step isothermal heat cycle on AC sample simulating SHT and artificial aging (left) and isochronal heating tests at 1 and 10°C/min performed on specimens in different initial conditions (right).

THERMAL DIFFUSIVITY

the density ρ and the specific heat cp: (D = λ/(ρ*cp)). The dif-

The results of temperature-dependent thermal diffusivity

fusivity in the alloy have roughly the same temperature trend

for the investigated alloy in three different initial conditions

as the thermal conductivity, at least in conditions where and

are shown in Figure 2. The thermal diffusivity (D) is directly

both density and cp have smooth and minor changes (for

correlated to the thermal conductivity (λ), and inversely to

example related to secondary phases).

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Fig.2 -Temperature-dependency of thermal diffusivity (D) for the investigated alloy in three different initial conditions. For each experimental condition, data taken during the heating and cooling parts of the cycle are plotted with different symbols (H and C, respectively) to highlight their differences.

Experimental data taken during the slow isochronous he-

originated by a unit change in temperature (coefficient of

ating and cooling are plotted with different symbols to hi-

thermal expansion) is not constant, but it shows peak/valleys

ghlight the correlation of thermal diffusivity to the actual

(Figures 3a and 3b) whose position depends on the initial

microstructural composition at the moment at which the

microstructural condition and heating rate. These changes

measurement was taken. During heating up to about 350-

can be correlated to the formation/dissolution of different

400°C, the three curves became closer. The trend of the

phases, whose specific volume differs from that of the ma-

curve is also the same during the slow cooling from 530°C.

trix. Thus, the amount of the phases present at each tempe-

The complete separation of temperature-only effects from

rature change the actual specimen length with respect to the

those related to microstructural changes is not possible in

general trend of a constant coefficient of thermal expansion.

these in-situ tests.

Specifically, in the case of casting Al-Si-Mg [9] and wrought

Nevertheless, the abovementioned correlation of diffusivi-

Al-Mg-Si alloys [10], where the amount of Si exceeds that for

ty to thermal conductivity and the Wiedemann–Franz law,

the only formation of precipitates of the β-Mg2Si sequence,

correlating which states that the ratio between thermal con-

the precipitation of secondary silicon particles with diamond

ductivity and electrical conductivity increases with tempe-

structure causes an increase of specimen length [9], while

rature [9], allow a simplified approach for thermal diffusivity

the formation of precipitates of β-Mg2Si and their dissolution

evolution. This can be considered as the overlapping of the

in Al-Mg- Si alloys do not correspond to any peak/valley in

decreasing trend for pure aluminium overlapped to changes

dilatometric curves [9].

related to alloying atoms in solid solution, as discussed for electrical conductivity. The approach allows comparison between these later trends and those for ex-situ electrical conductivity. In SHT condition, their solute atoms decrease more significantly with respect to initial content, provoking a large drop in the diffusivity values. Above 150-200°C, the data for initial conditions converge, with an increased effect of solute atoms that reduces diffusivity more rapidly than for pure aluminium [8].

DILATOMETRIC TESTS The results of dilatometric tests show that the thermal strain

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Scientific papers - Die casting

Fig.3 - Results of dilatometric tests performed at 1 and 10 °C/min heating rate on samples of the Al- Al7Si-0.5Cu-0,4Mg after Solution Heat Treatment (left) and after further aging at 230°C for 4 h (rigth).

The identification of peaks on the basis of dilatometric tests

into account, adding complexity to the modelling of thermal

only is not straightforward, as in DSC analyses.

diffusivity. Similar consideration could be done for dilato-

The peak of elongation corresponding to Si formation can

metric tests and for temperature-dependent electrical con-

help the identification of peaks in materials characterizations

ductivity tests (not considered here). Under less unstable

involving both techniques. In the present cases, DSC tests

conditions the material properties are also less affected by

and TEM analyses show that the nucleation of secondary Si

the heat cycle selected to investigate the temperature-de-

starts in a temperature range between 230°C and 280°C, and

pendence of properties (heating/cooling rates in isochronal

concurrently β” Mg5Si6 transforms into β’-Mg1.8Si [10]. This

tests). In age hardening alloys isochronal tests for one or a

is compatible with the upward peak obtained in the present

set of thermophysical properties could be also used as a tool

work on the SHT sample at 10°C/min and also to the absen-

to investigate by relatively simple tests, the microstructural

ce of the same peak in the specimen artificially aged for

changes taking place within the material,aiming for exam-

4 hours tested at the same heating rates. . The kinetics for the

ple at modelling their kinetics. The heating rates available

formation and dissolution of secondary Si and their related

for different property and equipment are often not overlap-

phases is a function of the heating rate: the higher the hea-

ping. Considering the thermal diffusivity, dilatometry and

ting rate, the higher temperature needed for precipitation of

calorimetric tests here mentioned, the latter are more often

secondary Si.

performed at low heating rates (0.2-6°C/min are for example reported in [7]), while the set heating rate can increase

CONCLUSIONS AND FINAL REMARKS

up to 40°C/min in several DSc equipment, with the smallest

The simple testing program carried out on the Al-7Si-Mg-

sample and furnace sizes. Without mentioning the advanta-

Cu alloy demonstrate that thermo-physical properties of

ges/disadvantages of adopting high or low heating rate for

age-hardenable alloys are both temperature- and micro-

different techniques, the adoption of a wider range for them

structure- dependent, with this latter effect being more si-

and the possibility of clear identification of microstructural

gnificant for the metastable SHT condition. The temperature

changes can help to study complex kinetics of phase tran-

dependence of thermal diffusivity of the three samples gives

sformations. Lastly, The possibility to carry out ex-situ te-

an example of this. From the point of view of material cha-

sts (in this case electrical conductivity) on a quenched mi-

racterization in view of making data available for the design

crostructure was observed to eliminate the temperature

of high-temperature, long-term service components, the

effect from that of the microstructural changes induced by

more stable aged/serviced material could be more suitable

isothermal or isochronous. This tool, allowing to operate

than initial unstable material. Alternatively, the progressive

with different heating rates, represents an additional tool for

change of properties during aging/service should be taken

the identification of thermal events-microstructural change

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and for modelling of these latter.

loys by Thermomechanical Processing. The Italian Ministry of Education, University and Research is acknowledged for

ACKNOWLEDGMENTS

the support through the Project “Department of Excellence

Authors want to thank the Christian Doppler Society for sup-

LIS4.0−Lightweight and Smart Structures for Industry 4.0”.

porting CD-Laboratory for Design of High-Performance Al-

REFERENCES [1] [2]

[3] [4] [5]

[6] [7] [8] [9] [10]

S. Roy, L.F. Allard, A. Rodriguez, T.R. Watkins, and A. Shyam, Comparative Evaluation of Cast Aluminum Alloys for Automotive Cylinder Heads: Part I – Microstructure evolution. Metall. Mater. Trans. A, 2017; 48; 2529-2542. Doi:10.1007/s11661-017-3985-1.

Chang-Yeol Jeong, High Temperature Mechanical Properties of Al¬Si¬Mg¬(Cu) Alloys for Automotive Cylinder Heads, Materials Transactions, 2013; 54; 588- 594. Doi: 10.2320/matertrans.M2012285.

Chomsaeng N, Haruta M, Chairuangsri T, Kurata H, Isoda S, Shiojiri M, HRTEM and ADF-STEM of precipitates at peak-ageing in cast A356 aluminium alloy, J. Alloys Comp. 2010; 496; 478-487.

Wang G, Sun Q, Feng L, Hui L, Jing C. Influence of Cu content on ageing behavior of AlSiMgCu cast alloys. Mater. Des. 2007; 28; 1001–1005. Doi: 10.1016/j.matdes.2005.11.015Zhang DL, Zheng L. The quench sensitivity of cast Al-7 Wt Pet Si-0.4 Wt pct Mg alloy, Metall. Mater. Trans. A. 1996; 27; 3983-3991. Doi:10.1007/BF02595647 Ram D-, Wang R, Krumphals F, Poletti MC, Gutierrez F, Stauder B. Effect of thermal treatment parameters on the age-hardening of AlSi7MgCu05 alloy. 26th Int. Student's Day of Metallurgy At: Wels, Austr, 2019.

Kemsies RH Dispersoidbildung und Dispersoidstabilität in Aluminium-ManganLegierungen. Dissertation zur Erlangung des akademischen Grades, 2019, Univ. Rodstock. Doi: 10.18453/rodoc_id00002511.

Leitner M, Leitner T, Schmon A, Kirmanj A, Pottlacher G. Thermophysical Properties of Liquid Aluminum. Metall Mater Trans A 2017; 48; 3036–3045.

Lasagni F, Falahati A, Mohammadian-Semnani H, Degischer HP. Precipitation of Si revealed by dilatometry in Al-Si-Cu/Mg alloys.

Kovove Mater. 2008; 46; 1–6.

Kumar M, Poletti C, Collet C, Degiscer HP, Precipitation Kinetics in Age-Hardening by Dilatometry and Differential Scanning Calorimetry. Proc. ICAA 12 Conf, Yokohama (Japan) 2010, 1009-1014.

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Scientific papers - Die casting

Effects of bismuth on the characteristics of eutectic Si particles in Na-modified A356 alloys O. Gursoy , G. Timelli

In this work, the effect of bismuth over Na-modified eutectic Si particles was investigated in an A356 alloy with different Bi and Na contents. Metallographic and thermal analysis techniques were used to examine the microstructural changes occurring at different Bi and Na levels. The cooling curves and the corresponding derivative curves were plotted to determine the nucleation TN, minimum TMin and growth TG temperatures for the Al-Si eutectic reaction. The results indicate that the TN, TMin and TG values decrease after Na modification. In the unmodified alloy, the eutectic Si shows a fully unmodified lamellar morphology. A fully modified structure is obtained with 55 ppm Na in the alloy containing 20 ppm Bi impurity, while the same level of Na can partially modify the alloy containing 200 ppm Bi. It was also determined that the Bi-Na-rich intermetallic in the microstructure causes counteraction and it can be a binary or triple eutectic system containing more than one compound.

KEYWORDS: BISMUTH, SODIUM, EUTECTIC MODIFICATION, THERMAL ANALYSES, COUNTERACTION

INTRODUCTION Secondary aluminium alloys have generally a lower production cost than primary ones. However, different impurity elements coming from the recycling process can affect the mechanical properties of the final product. To reduce the level of the impurities, the dilution is carried out by mixing secondary and primary aluminium alloys; however this route appears nowadays expensive and difficult to pursue.

Most of the secondary aluminium alloys come from a combination of casting and wrought alloys. Both scraps may contain bismuth as a trace element, and this may be faced with the harmful effects of the existence of bismuth impurity. The main source of Bi impurity in the Al-Si alloys is Bi

Ozen Gursoy, Giulio Timelli University of Padova, DTG, Italy

containing free-machining wrought aluminium alloys [1].

Bismuth addition has an important advantage on the machinability of Al alloys. Thanks to their low melting points, Bi-rich phases act as a lubricant and decrease the cutting force during the machining process [2,3]. Bismuth is also known as a chemical refiner for the eutectic silicon structure in hypoeutectic and hypereutectic Al-Si alloys, and it provides higher wear resistance and tensile performance [4].

After the recycling process, Bi may remain as an impurity element and counteract the effect of further additions or La Metallurgia Italiana - November/December 2021

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preliminary molten metal treatments. Some authors repor-

rore. L'origine riferimento non è stata trovata.. If present,

ted [5,6] that the presence of Bi in Sr-modified Al-Si cast

bismuth was below the lower detection limit (< 15 ppm) of

alloys increases the eutectic growth temperature and leads

OES in the base alloy. About 3 kg of ingot pieces were mel-

towards a fibrous to flake transition of eutectic Si particles

ted in a SiC crucible using an electric furnace at 730 ± 5 °C.

with a decrease of tensile performance, especially in elon-

For the investigation of Na-Bi interaction, the melt was al-

gation [7,8]. Some complex phases, such as BiSr, Bi2Sr3, Mg-

loyed with different Na (0 and 55 ppm) and Bi (20 and 200

Bi2Sr forming by Bi-Sr interactions, reduce the available Sr

ppm) levels by adding metallic sodium and AlBi9 master

amount for eutectic modification [5,9]. Furthermore, Bi has

alloy, respectively. The contact time between the elements

a great oxidation tendency and forms a Bi-rich oxide surface

and the melt was about 15 min. The final experimental alloys

covering the molten bath [5] and thus preventing the forma-

are listed in Table 2. The molten metal was carefully poured

tion of a continuous Al oxide surface [10].

into a BN-coated steel cup which was pre-heated at 700 ± 5

Sodium is the most effective eutectic Si modifier in Al-Si al-

°C.

loys. Multiple twinning reactions during eutectic Si growth

To monitor the solidification path and determine the cha-

and increasing the twin density can be achieved by adding a

racteristic temperatures of the experimental alloys, compu-

low amount of Na (<100 ppm) [11,12]. Na addition is general-

ter-aided thermal analysis technique was used, which was

ly applied to change the morphology of eutectic silicon cry-

based on the two-thermocouple method. The tip of K-type

stals by flake-to-fibrous transition resulting in a significant

thermocouples (ø1 mm), which were covered with steel

improvement of mechanical properties [13].

tubes, were fixed at the lid of the cup and inserted into the

Studies on the effect of Na-Bi interaction in Al-Si alloys are

melt after pouring. The specimens were solidified in air with

limited, even though separately additions have been inve-

a cooling rate of ~0.2 °C/s. A high-speed data acquisition sy-

stigated. This work aims to study the effect of Bi impurity

stem with a sampling rate of 0.1 s-1 and an analogue-to-digi-

over Na-modified AlSi7Mg0.3 alloy, focusing on possible

tal converter accuracy of 0.1 °C was used. The data from the

variations in the solidification sequence and microstructure

central thermocouple were processed for each experimen-

of the alloy.

tal alloy to determine the cooling curve and the characteri-

2

stic temperatures by using the derivative curves (dT/dt) of the cooling curves.

EXPERIMENTAL PROCEDURE In the present study, an AlSi7Mg alloy (A356.2) was used as a base alloy and the chemical composition, measured by an optical emission spectrometer (OES), is listed in Table 1Er-

Tab.1 - Chemical composition of the investigated alloy (mass %).

Si

Fe

Cu

Mn

Mg

Ti

Na

Bi

Al

7.5

0.0564

0.0031

0.0022

0.251

0.128

0.0001

-

Bal.

The eutectic nucleation temperature (TN,eu), the minimum

experimental alloy and it was recognized that the variation

temperature of eutectic (Tmin,eu), and the eutectic growth

of the characteristic temperatures during solidification was

temperature (TG,eu) were analyzed to study the efficiency of

less than 1 °C.

the eutectic modification and the possible Na-Bi interaction.

At least three thermal analysis tests were carried out for each

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Tab.2 - Nominal and actual Na and Bi contents in the different experimental alloys.

Nominal Na addition

Nominal Bi addition

Actual Na addition

Actual Bi addition

Na0Bi20

0

20

0

25

Na55Bi20

55

20

48

20

Na0Bi200

0

200

0

184

Na55Bi200

55

200

58

229

Alloy

(PPM)

(PPM)

(PPM)

(PPM)

The samples for microstructural investigation were drawn

temperatures in the region of the Al-Si eutectic reaction of

from the location close to the tip of the central thermocou-

the experimental alloys containing different amounts of Na

ple in order to correlate the microstructure with the results

and Bi are shown in Fig. 1. The eutectic plateau of the Al-

obtained from thermal analysis. A standard metallographic

Si7Mg base alloy is steady at 575.1 °C, while the nucleation

procedure was used for samples’ preparation. Microstructu-

of eutectic Si takes place at 577.7 °C. The eutectic Si in the

ral investigations were carried out by using an optical micro-

Na0Bi20 and Na0Bi200 alloys, both containing Bi impurity,

scope (OM) and a field emission gun scanning electron mi-

nucleates at gradually higher temperatures with increa-

croscope (FEG-SEM) equipped with an energy-dispersive

sing Bi level, and the solidification paths of these alloys are

spectrometer (EDS) and then quantitatively analyzed using

plotted at higher temperatures (see Fig. 1). This behaviour

an image analyzer. These investigations were focused on the

is generally related to the formation of a precursor that can

morphological variation of the eutectic Si.

favour the nucleation of the eutectic Si at higher temperature. Therefore, the addition of Bi leads to the precipitation of

RESULTS AND DISCUSSION

active nucleation sites for eutectic Si.

The solidification path and the variation of the characteristic

Fig.1 - (a) Cooling curves and (b) variation of the characteristic eutectic temperatures of the experimental alloys.

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Sodium modification depresses the eutectic plateau of the

55Bi200 alloy. The slight slope which is visible where the eu-

unmodified alloys, as shown in Fig. 1a. The cooling curve

tectic plateau begins on the solidification path of Na55Bi20

of Na55Bi20 alloy shows a greater depression than the Na-

alloy may be caused by the precipitation of Fe-rich phase.

Fig.2 -Microstructures of the alloys: (a) Na0Bi20, (b) Na55Bi20, (c) Na0Bi200 and (d) Na55Bi200.

The eutectic Si in the alloys with Bi impurity nucleates at

is fully modified after 55 ppm Na addition (Fig. 2b). However,

higher temperatures (TN,eu) than the base alloy; further, the

55 ppm Na addition is not sufficiently effective to modify the

eutectic growth temperature (TG,eu) shows higher values by

200 ppm Bi-containing alloy; this Na amount can only par-

increasing the Bi content. In the alloy containing 20 ppm Bi,

tially modify the eutectic structure (Fig. 2d) when the level of

the TN,eu decreases from 581.0 to 574.1 °C, while the TG,eu de-

Bi impurity has increased to 200 ppm. Even though the size

creases from 578.1 to 569.3 °C after Na addition. In the alloy

of the eutectic Si is reduced, particles with plate-like shape

with 200 ppm Bi impurity, the TN,eu decreases from 581.4 to

are visible in the microstructure (Fig. 2d). The addition of Na

580.8 °C, while the TG,eu decreases from 579.3 to 574.1 °C,

in Al-Si alloys has been demonstrated to change the shape

after Na addition. The efficiency of Na modification on the

of eutectic Si crystals from flake to fibrous morphology. In

decreasing the characteristic eutectic temperatures is hi-

the Bi-containg alloys, the AlP compounds, which are the

gher when the level of Bi impurity is low. It can be claimed

main nucleant for eutectic Si, seem to not be completely

that Bi impurity prevents the decrease of the characteristic

deactivated after Na addition; this is due to the interaction

temperatures.

between Na and Bi. Therefore, Si crystals can nuleate over

Fig. 2 shows the microstructure of the experimental alloys.

AlP phase and form coarse flakes. It can be concluded that

While the Si flakes are coarse in the microstructure of Na-

the effective amount of Na element to modify the eutectic Si

0Bi20 alloy (Fig. 2a), the eutectic structure of Na55Bi20 alloy

is decreased by Bi impurity.

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Coarse blocky Si crystals are seen in unmodified and Bi-con-

Figs. 3b and 3c show EDS point mode and line-scan mode

taining alloys (Na0Bi20, Na0Bi200). The microstructure of

analyses of the Bi-bearing phase shown in Fig. 3a. Although

Na-modified alloy containing 200 ppm Bi impurity was in-

Al, Si, Mg, Bi and Na are detected in EDS point mode analy-

vestigated in detail by scanning electron microscopy (Fig.

sis, only Mg, Bi and Na peaks are observed in line-scan one.

3). Bi-rich intermetallics appeared as bright dots due to the

Al and Si counts are most likely due to the matrix and eu-

high atomic mass of Bi element at the centre of coarse eu-

tectic Si particle. It can be claimed that the bright particle

tectic Si crystals. It is observed that these bright particles are

contains Na and Mg elements as well as Bi.

surrounded by or vicinity of coarse eutectic silicon particles.

Fig.3 - SEM images of an eutectic Si crystal with a centrally located Bi-rich particle in the Na55Bi200 alloy at (a) low and (d) high magnifications; EDS (b) point mode and (c) line-scan mode analyses of the particle.

When the Bi-Na-rich phase is investigated at higher magni-

CONCLUSION

fication (see Fig. 3d), it is observed that light grey primary

In the current work, the effect of Bi impurity on Na-modi-

columns are positioned at an angle of 108° angles to each

fied eutectic Si particles was investigated in A356 alloywith

other in the white matrix. The Al-Bi phase diagram demon-

different Bi and Na contents. The following conclusions can

strates that the solubility of Bi in the α-Al phase is less than

be drawn.

0.24 wt.% at 657 °C and almost null at the eutectic tempera-

• The characteristic temperatures of eutectic reaction in-

ture (270 °C) [14]. The EDS analyses indicated also the exi-

crease with increasing level of Bi impurity in AlSi7Mg alloy.

stence of Mg and Na elements in the Bi-bearing phase. The

• Bi impurity decreases the effectiveness of Na-modifica-

high magnification of the centrally located Bi-rich particle

tion of eutectic Si.

shows a complex structure that appears as a binary or ter-

• Bi-Na interaction leads to the formation of Bi-Na-rich

nary eutectic structure (Fig. 3d). Considering the Mg-Bi and

rich phases.

Bi-Na phase diagrams [14], the structures might composed

• In case of higher level of Bi impurity, more Na addition is

by Bi2Mg3, as previously reported in [15], and BiNa which can

required to fully modify the eutectic Si.

counteract the modification effect of Na reducing the active Na element in the system.

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ACKNOWLEDGEMENTS This research was developed with the financial support of Fondazione Cassa di Risparmio di Padova e Rovigo (CariPaRo).

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8]

[9] [10] [11] [12] [13] [14] [15]

BSI Standards Publication Aluminium and aluminium alloys — Wrought products — Temper designations 2017.

Barzani, M. M., Sarhan, A. A., Farahany, S., Ramesh, S., & Maher, I. Investigating the Machinability of Al–Si–Cu cast alloy containing bismuth and antimony using coated carbide insert. Measurement, 2015;62, 170-178.

Timelli, G., & Bonollo, F. Influence of tin and bismuth on machinability of lead free 6000 series aluminium alloys. Materials Science and Technology, 2011;27(1), 291-299.

Pereira, C. L., Gomes, L. F., & Spinelli, J. E. Effects of Bi addition on Si features, tensile properties and wear resistance of hypereutectic Al-15Si alloy. In IOP Conference Series: Materials Science and Engineering, IOP Publishing 2020 May;861, No. 1, p. 012056.

El-Hadad, S., Samuel, A. M., Samuel, F. H., Doty, H. W., & Valtierra, S. Effects of Bi and Ca addition on the characteristics of eutectic Si particles in Sr-modified 319 alloys. International Journal of Cast Metals Research, 2003;15(5), 551-564.

Farahany, S., Ourdjini, A., Idris, M. H., & Thai, L. T. Poisoning effect of bismuth on modification behaviour of strontium in LM25 alloy.

Bulletin of Materials Science, 2011;34(6), 1223-1231.

Farahany, S., Idris, M. H., & Ourdjini, A. Effect of bismuth and strontium interaction on the microstructure development, mechanical properties and fractography of a secondary Al–Si–Cu–Fe–Zn alloy. Materials Science and Engineering: A, 2015;621, 28-38.

Mohamed, A. M. A., Samuel, F. H., Samuel, A. M., & Doty, H. W. Effects of individual and combined additions of Pb, Bi, and Sn on the microstructure and mechanical properties of Al-10.8 Si-2.25 Cu-0.3 Mg alloy. Metallurgical and Materials Transactions A, 2009;40(1), 240-254.

Farahany, S., Dahle, A. K., Ourdjini, A., & Hekmat-Ardakan, A. Flake-fibrous transition of silicon in near-eutectic Al-11.7 Si-1.8 Cu-0.8 Zn-0.6 Fe-0.3 Mg alloy treated with combined effect of bismuth and strontium. Journal of Alloys and Compounds, 2016;656, 944-956.

Papworth, A., & Fox, P. The disruption of oxide defects within aluminium alloy castings by the addition of bismuth. Materials letters, 1998;35(3-4), 202-206.

Li, J. H., Albu, M., Hofer, F., & Schumacher, P. Solute adsorption and entrapment during eutectic Si growth in A–Si-based alloys. Acta materialia, 2015;83, 187-202.

Gursoy, O., & Timelli, G. Lanthanides: A focused review of eutectic modification in hypoeutectic Al–Si alloys. Journal of Materials Research and Technology, 2020;9(4), 8652-8666.

Sigworth, G. K. The modification of Al-Si casting alloys: important practical and theoretical aspects. International Journal of Metalcasting, 2008;2(2), 19-40.

Baker, H., & Handbook, A.S.M. Vol. 3: Alloy Phase Diagrams. ASM International Materials, Ohio, 1992; pp. 284-499.

Ferraro, S., Timelli, G., & Fabrizi, A. Effects of bismuth on the microstructure and mechanical properties of AlSi9Cu3 (Fe) die casting alloys. In Materials Science Forum Trans Tech Publications Ltd. 2013;765, pp. 59-63.

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Scientific papers - Die casting

Fatigue properties and microstructural analysis of diecast AlSi11Cu2(Fe) alloy: effect of surface finishing M. Merlin, D. Benasciutti, L. Lattanzi, A. Fortini, G. Timelli

In the present work, a secondary AlSi11Cu2(Fe) alloy was diecast by means of a specifically designed die. Specimens with both the as-diecast surface quality and after sand-blasting were prepared and subjected to uniaxial fatigue tests in order to investigate the effect of surface finishing on S-N curves. The S-N curves for the two different surface finishing were estimated and compared in terms of inverse slope k and amplitude strength σA at 5×106 cycles. Experimental data for the two different surface finishing showed a similar statistical dispersion in fatigue life. Nevertheless, amplitude strength σA = 73 MPa and S-N slope k = 25.8 were obtained for sand-blasted samples, which are higher than the corresponding σA = 62 MPa and k =

11.4 showed by the as-diecast samples. After fatigue testing, both fracture profiles and surfaces were studied by optical and scanning electron microscopy to correlate crack initiation and propagation with fatigue strength. The crack initiation sites

were localised mainly along the die separation-line in the as-diecast surface finishing condition, while, for the sand-blasted samples, an essential role in crack initiation was played by casting defects such as oxide films and porosities.

KEYWORDS: DIECAST ALUMINIUM ALLOY – FATIGUE TESTS – CASTING DEFECTS – SAND-BLASTING – MICROSTRUCTURE

INTRODUCTION In the automotive industry, aluminium-silicon alloys are broadly used due to their high strength to density ratio and corrosion resistance. For the production of structural components with complex geometry and near net shape, high-pressure diecasting (HPDC) process is the most used.

Despite in recent years a lot of work has been carried out to improve the quality of cast parts, the main drawback of components produced with HPDC remains the presence of defects. In particular, oxide films, gas and shrinkage porosity, cold shots, and micro or macro segregations are common defects usually affecting the mechanical properties of casting products to some extent. In literature, static and fatigue properties of high-pressure diecast specimens have been deeply studied. Avalle et al [1] showed that the porosity level of high-pressure diecast AlSi9Cu3(Fe) samples in the as-diecast condition controls the properties of the material and that tensile strength decreases linearly with

M. Merlin

Department of Engineering (DE), University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy - mattia.merlin@unife.it, telephone number: + 39 0532 974831

D. Benasciutti

Department of Engineering (DE), University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy

L. Lattanzi

Department of Engineering (DE), University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy

A. Fortini

Department of Engineering (DE), University of Ferrara, Via Saragat 1, I-44122 Ferrara, Italy

G. Timelli

Department of Management and Engineering (DTG), University of Padova, Stradella S. Nicola 3, I-36100 Vicenza, Italy

the porosity content. The same authors dealt with the fatigue properties of the samples considering the effect of the as-diecast surface finishing. It is well known that the presenLa Metallurgia Italiana - November/December 2021

pagina 79

Memorie scientifiche - Pressocolata ce of internal defects can surely affect the fatigue behaviour

In this study, with the aim to improve the knowledge on

of diecast aluminium components, but they found that the

how both the as-diecast and sand-blasted surface finishing

resistance to fatigue loadings is mainly driven by external or

as well as the microstructure interact with the fatigue crack

subcortical defects as well as by roughness. The influence of

initiation and propagation, diecast AlSi11Cu2(Fe) samples

porosity on the fatigue strength of an AlSi9Cu3 high-pressu-

were fatigue tested under uniaxial constant amplitude lo-

re diecast aluminium alloy was also studied by J. Linder et al.

ads at various stress levels. After fatigue testing, fractured

[2], with the aim to derive the influence of defect size with

samples were investigated by optical microscopy (OM) and

respect to the fatigue load.

scanning electron microscopy (SEM) in order to understand

A. Nourian-Avval et al. [3] evaluated the fatigue behaviour of

the role of surface finishing, microstructure and defects on

A356 aluminium alloy specimens obtained by HPDC, in the

fracture initiation and propagation.

as-diecast surface condition and considering the effect of the T6 heat treatment. They found that almost all the fatigue

MATERIAL AND METHODS

failures originated from pores at or near the surface, even

Sample preparation

though some fatal pores were randomly distributed in the

Multi-specimen castings, composed of specimens for diffe-

entire cross section.

rent mechanical tests, were performed using a specifically

In light of these studies, the fatigue behaviour of diecast alu-

designed die in a cold-chamber diecasting machine [4]. The

minum alloys in the as-diecast finishing condition has beco-

locking force of the diecasting machine together with the

me of interest. In fact, fatigue tests are usually performed on

other process parameters are collected in Table 1. An AlSi-

machined samples, i.e. without taking into account the real

11Cu2(Fe) (EN AC-46100) alloy according to standard che-

finishing and the presence of sub-cortical defects typically

mical composition was used to produce the castings.

of diecast components.

Tab.1 - HPDC process parameters.

Looking force

2.9 Mn

Regime die

First phase plunger velocity

plunger velocity

Second phase

Third phase

~ 230 °C

0.2 m/s

2,7 m/s

40 Mpa

temperature

pressure

In this investigation, unnotched cylindrical specimens with a

FATIGUE TESTS

nominal diameter of 6 mm underwent fatigue tests. One half

Uniaxial constant amplitude fatigue tests were performed

of specimens were maintained in the as-diecast surface con-

by an Italsigma LM10 (Italsigma, Forlì, Italy) servo-hydraulic

dition, i.e. with surface details such as flashes. A three-cycle

testing machine with a 20 kN load cell and at a load control

sand-blasting was performed on the other half of speci-

with a frequency of 28 Hz. A stress ratio R = 0.1, which cor-

mens. The standard procedure on this alloy is a one-cycle

responds to a tension-tension cycle with 𝜎min=0.1∙𝜎max, was

sand-blasting. Before fatigue testing, the arithmetic average

chosen. In order to set up the different load levels, the ave-

surface roughness (Ra) of 0,62 ± 0,10 and 6,42 ± 1,13 was

rage static properties in terms of yield strength (152 ± 5 MPa)

sted specimens, respectively.

collected in Table 2, all fatigue tests were carried out with

measured by a Handysurf E-35 (Zeiss, Oberkochen, Germany) stylus roughness tester on as-diecast and sand-bla-

and ultimate tensile strength (303 ± 4 MPa) were firstly evaluated. In light of this, and according to the load conditions

stress amplitudes between 65 MPa and 82 MPa; a number of cycles equal to 1∙107 was considered as the ‘run-out’ value.

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Scientific papers - Die casting

Tab.2 - Fatigue tests set up. σa [MPa]

Δσ [MPa]

σmax [MPa]

σmin [MPa]

σm [MPa]

65

130

72

144

160

16

88

74

148

164

16

90

75

150

167

17

92

78

156

173

17

95

80

160

178

18

98

82

164

182

18

100

144

14

79

MICROSTRUCTURAL ANALYSIS

RESULTS AND DISCUSSION

After fatigue testing, preliminary observations of the fracture

Fatigue tests

surfaces of all the tested samples were carried out by a Leica

Figure 1 displays the results of the fatigue tests for both the

MZ6 (Leica, Weztlar, Germany) stereomicroscope in order

as-diecast and the sand-blasted samples. The S-N curves for

to identify at low magnifications the potential initiation sites

the two different surface finishing were estimated in terms of

and macro-defects which might have played a significant

the inverse slope k of the linear regressions. The amplitude

role in determining the mechanical behaviour of the mate-

strength σA at 5× 106 cycles was assessed, as well as the scat-

rial. Microstructural investigations were then performed by

ter bands at 10% and 90% of survival probability. Regardless

a Leica DMi8A (Leica, Wetzlar, Germany) optical microscope

of the surface finishing, the results show a similar statistical

and a Zeiss EVO MA 15 (Zeiss, Oberkochen, Germany) scan-

dispersion in fatigue life. The values of amplitude strength σA

ning electron microscope to study the main microstructural features involved in both fracture initiation and propagation.

= 73 MPa and S-N slope k = 25.8 obtained for sand-blasted

samples are higher than the corresponding σA = 62 MPa and k = 11.4 shown by the as-diecast samples.

Fig.1 - S-N curves for as-diecast and sand-blasted specimens.

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Memorie scientifiche - Pressocolata

MICROSTRUCTURAL INVESTIGATIONS

the material were studied by OM on both longitudinal and

The results of fatigue tests were subsequently analysed and

transverse sections of the samples (Fig.2). Casting defects

interpreted on the basis of microstructural investigations

typically of high-pressure die-casting process were de-

conducted by stereomicroscopy, OM and SEM.

tected.

Before fatigue testing, the main microstructural features of

Fig.2 - OM micrographs of typical casting defects observed in the as-diecast samples: a) lamination and b) air/gas porosities.

In particular, the presence of lamination near to the casting

ce finishing induced by sand-blasting, in agreement with the

surface (Fig.2a) as well as air/gas porosities close to the cen-

measured roughness values. Moreover, the microstructure

tre (Fig.2b) of the samples were observed; these defects can

of the sand-blasted sample is clearly modified for the thick-

strongly affect the dynamic mechanical properties of the al-

ness of a few tens of microns below the surface. This may

loy.

explain the improved fatigue behaviour of the alloy obtained

The micrographs of the longitudinal sections of as-diecast

in the fatigue tests (Fig.1).

and sand-blasted samples in Fig.3 show the different surfa-

Fig.3 - OM microstructure and surface finishing of the longitudinal section of a) as-diecast and b) sand-blasted samples.

After fatigue testing, preliminary investigations of the fractu-

that played a significant role in the fracture mechanism. Fi-

re surfaces were carried out by stereomicroscopy in order

gure 4 depicts the images of the fracture surfaces of four dif-

to identify the fracture initiation sites and the macro-defects

ferent tested samples with detail at higher magnification of

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Scientific papers - Die casting

the initiation site. The number of cycles at failure for each

by the highest number of cycles at failure and the initiation

sample is also highlighted in Fig.2. Among all the tested

site can be identified as an internal defect.

samples, the sand-blasted sample in Fig.4c is characterised

Fig.4 - Fracture surfaces of four different samples: a,b) as-diecast and c,d) sand-basted samples.

Fractographic analysis performed by SEM showed that, for

Considering the sand-blasted samples (Fig.5e and 5g), the

as-diecast samples, the surface defects or sub-cortical po-

crack mainly initiated from internal defects such as poro-

res provided sites for fatigue crack initiation. In Fig.5a it is

sities (Fig.5f) or cold joints (Fig.5d), generated by the die-

possible to observe that the initiation of the fatigue fractu-

casting process; overall, the samples that showed a longer

re occurred at the flash generated by the parting line of the

fatigue life were those with the crack initiated from internal

die (Fig.5b). In other samples, the initiation of the crack is

defects. This result is due to the compressive stress on the

promoted by the presence of sub-surface defects, such as

surface defects that is caused by sand-blasting.

porosities (Fig.5c and 5d).

Fig.5- Fracture surfaces of four different samples: a,b) as-diecast and c,d) sand-basted samples.

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Memorie scientifiche - Pressocolata

CONCLUSIONS

FUNDING

In this work, uniaxial constant amplitude fatigue tests with

This work was partially funded by the European Project

stress ratio R = 0.1 were performed on AlSi11Cu2(Fe) diecast

NADIA (New Automotive components Designed for and

specimens and the effect of sand-blasting in improving the

manufactured by Intelligent processing of light Alloys, NM-

fatigue behaviour of the alloy was evaluated. Regardless of

P-2004-SME 3.4.4.5, contract n.026563-2) and by FIR 2018,

the surface finishing, the results show a similar statistical di-

Prot. n. 117696 of the University of Ferrara (Italy)

spersion in fatigue life, even though the amplitude strength and S-N slope for sand-blasted specimens resulted higher than the corresponding ones for the as-diecast specimens.

Microstructural investigations confirmed that crack initiation sites in as-diecast specimens are preferentially localised on the surface or on sub-cortical defects, while in sand-blasted ones also internal defects provide sites for fatigue crack initiation.

REFERENCES [1] [2] [3] [4]

Avalle M et al. Casting defects and fatigue strength of a die cast aluminium alloy: a comparison between standard specimens and production components. Int. J. Fatigue; 2002;24:1-9 Linder J at al. The influence of porosity on the fatigue strength of high-pressure die cast aluminium. Fatigue Fract. Engng, Mater. Struct.; 2006;29:357-363 Nourian-Avval A et al. Fatigue design with high pressure die casting aluminum including the effects of defects, sectin size, stress gradient, and mean stress. Mater. Today Commun.; 2020;25:101567 Lattanzi L et al. Effects of microstructure and casting defects on the fatigue behaviour of the high-pressure die-cast AlSi9Cu3(Fe) alloy. 3rd International Symposium on Fatigue Design and Material Defects (FDMD). 2017 Sept 19-22; Lecco, Italy. Structural Integrity Procedia. 2017;7:505-512

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Industry news - Attualità industriale

Micro Spray technologies for an efficient die spraying in HPDC edited by: M. Lutz

The potential for savings in an HPDC process is getting smaller and smaller. The areas where it is still possible to make significant improvements are thermoregulation and die spraying (which are closely related and interlocked). Nowadays, all foundries are able to implement effective spraying, but is this spraying efficient? Effectiveness shows the ability to achieve the set goal, while efficiency shows the ability to achieve the set goal with the least amount of resources. As far as die spraying is concerned, new release agents (oils or concentrates) are now available on the market that change the spraying philosophy: Whereas in the past spraying was used to cool the die surface, today spraying is used only to create the release film between the die and the casting. In this case, the differentiator is the technology used to apply these products: To achieve maximum results, the release agents must be micro-dosed. The precision and repeatability of micro-spraying is crucial and can only be achieved with appropriate technologies. WOLLIN's ECO spraying technology can reach the goal in different ways, adapting to the different needs of the foundry (long-term production or frequent die changes): the experience developed in recent years allows to successfully manage a wide range of projects. The objectives are multiple: reduction of cycle time; reduction of release agent, water and air consumption; longer life and higher availability of the die; better quality of castings and reduction of scrap.

KEYWORDS: ECOSPRAY, MICROSPAY, EFFICENCY, QUALITI, COST-SAVING INTRODUCTION: EFFICIENCY IN DIE CASTING The die casting process has been established for many years and itself offers little potential for further savings.

It is essentially the periphery that continues to offer opportunities for optimization. In addition to more efficient furnaces, explicit mention should be made here of die tempering, as well as the spraying process. The development of multi-circuit temperature control units in which each individual cooling channel can be controlled, the use of jet cooling systems, the use of 3D printing in die production, and new, more temperature-resistant release agents are resulting in new approaches to the spraying

Martin Lutz

Wollin GmbH; Germany

process.

This is significantly improved when it only has to ensure good release properties and good demouldability.

REQUIREMENTS PROCESS TECHNOLOGY It should not be concealed that a conversion of the casting processes requires a lead time of one to two years and ties up capacities in process technology. Those who

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Attualità industriale - Industry news

take this on will be rewarded with more stable processes,

This means that the temperature difference of the die

a reduction in the scrap rate and better casting surfaces.

between the filling phase and the solidification phase is significantly lower. Thanks to die temperature control

DIE TEMPERATURE CONTROL

channels close to the die and the use of jet cooling sy-

The use of effective water- and oil-based multi-channel

stems for squeezers and hotspots, cooling of the die by

die temperature control systems enables a casting pro-

the spraying process is no longer necessary today.

cess that is much more thermally stable than in the past.

Fig.1 -Die tempering.

The significantly lower cooling of the die saves energy,

has been removed and sprayed, so it does not have to be

since the die has lost much less heat energy after the part

supplied again.

Fig.2 -Die temperature before and after Spraying.

SEPARATING AGENT

chine contamination, clean surfaces and reduced scrap

The new water- or oil-based release agents developed

rates.

in recent years allow a significantly wider temperature spread of up to 400 °C. Depending on the application,

SPRAY PROCESS

wax-containing, wax-free or even wax-reduced release

For an optimal result in micro spraying, a few things are

agents are offered. What they all have in common are very

helpful. Ideally, a spraying machine with a high payload

good release properties. Wax-reduced release agents ad-

is used, which can support a mask spraying tool adap-

ditionally offer improved demoulding lubrication, as well

ted to the die. Separate pressure control for blowing and

as a significant improvement in surface quality, low ma-

spraying air is also advantageous for a good result, as is

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Industry news - Attualità industriale

a booster station for control air pressures of up to 8 bar;

ring spraying. Patented dosing nozzles are used for mi-

Wollin also offers retrofit solutions for this.

cro-spraying, which are offered with different dosing vo-

When the spraying tool is moved into the die, the two

lumes so that a suitable release film is achieved for each

die halves are blown out at high pressure. The masking

part of the die.

tool, which is adapted to the die and equipped with DDV nozzles, ensures uniform release agent application du-

Fig.3 -Mask spray tool.

Experience shows that the release agent concentrates avai-

lable on the market have excellent flow properties, so that

even areas of the die that are difficult to reach receive sufficient release agent. The release agent is applied in a pulse by

which the release agent in a chamber of the spray nozzle is

sprayed into the die under high pressure in very fine atomized form. The air pressure must not be set too high so that

the release agent is sprayed onto the die and does not evaporate without effect. Contrary to initial assumptions, ionization of the release agent and die is not only not necessary,

but in many cases rather a hindrance. Due to the course of the field lines, most of the release agent is deposited in the foremost area of the die.

Due to the fine atomization of the release agent, there is practically no Leidenfrost effect with microspraying.

Another advantage of applying only the amount of release

agent required for the release effect is that only very small amounts of substances are measured in the air.

Afterblowing after spraying is unnecessary, since no excess water was sprayed. The formation of cracks due to thermal

shock during conventional spraying is avoided, resulting in a significant extension of the die service life.

QUALITY

The lack of water during spraying enables a more even distri-

significant improvement in part quality. The surface and the microstructure become significantly more homogeneous, practically no blowholes are formed, and porosity is reduced to a minimum.

ENVIRONMENTAL ASPECT

Significant savings can be achieved through the contemporary form of spraying using EcoSpray. Today, awareness

of environmentally compatible and resource-saving pro-

duction is greater than ever. The aluminum industry already has a major advantage here thanks to the very good recycla-

bility of die castings. However, the classic casting process has a not inconsiderable impact on the environment, which

is also reflected in the costs. These include the energy costs incurred by cooling and reheating the dies, and the enor-

mous consumption of water and compressed air during spraying.

With microspraying, on the other hand, only very small

quantities of the release agent are evaporated, no fresh water is required and, crucially, no waste water is produced.

The consumption of energy-intensive compressed air is reduced enormously.

This makes the die casting process much better in terms of its climate footprint.

bution of the release agent in the die, which contributes to a La Metallurgia Italiana - November/December 2021

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Attualità industriale - Industry news

Tab.1 - Saving.

Wollin Eco Spray savings:

Acronimo

Energy savings (tempering of die cast mould)

50-70%

Compressed air (vol.)

50-70%

Fresh water

100%

Waste water

100%

COST FACTOR

tion is significantly minimized. The expensive disposal of

The environmentally friendly process of micro-spraying

waste water is completely eliminated. New foundries are

also has the advantage that it achieves significant cost be-

already being designed without the equipment for waste

nefits with only slightly higher investment costs for the

water disposal.

dies and their temperature control. The energy savings in

By eliminating the need for afterblowing during the

die temperature control often achieve a return on invest-

spraying process, up to 10 seconds or more of cycle time

ment in just a few months, the generation of compressed

can be saved. The extension of the die service life also

air is very expensive, a saving of 50-70% offers enormous

provides significant savings for the maintenance or re-

financial savings.

newal of the dies.

The costs for fresh water treatment are eliminated, the release agent mixing in the foundry is no longer necessary.

In addition to cost savings, the risk of bacterial contaminaTab.2 - Example Cost Savings.

Oil pan for automotive industry

Water based medium

EcoSpray with concentrate

Weight of the casting (complete)

15.000 g

15.000 g

Cycle time

82 sec

77 sec

Medium

1,8 l/cycle

5 ml/cycle

Reject Parts

4%

0,9 %

Waste water

100%

100%

Cost Savings total / year

197.000,- €

Water/Waste water

14.000,- €

Die life time (+50%)

77.000,- €

Cycle time

25.500,- €

Reject parts

80.500,- €

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Eventi AIM / AIM events CONVEGNI 27° Convegno Nazionale Trattamenti Termici – Genova, 26-27 maggio 2022 http://www.aimnet.it/tt.htm ESSC & DUPLEX 2021 - 11th European Stainless Steel Conference Science & Market & 8th European Duplex Stainless Steel Conf. & Exhib. – Lago di Garda, 15-17 giugno 2022 http://www.aimnet.it/essc.htm 39° Convegno Nazionale AIM – Padova, 21-23 settembre http://www.aimnet.it/nazionaleaim

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ROLLING 2022 - 12th International Rolling Conference - ottobre 2022

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FORMAZIONE E AGGIORNAMENTO IN PRESENZA (con possibilità di collegarsi da remoto) Giornata di Studio IL RUOLO DEI MATERIALI NELL’ECONOMIA DELL’IDROGENO – Milano, 27 gennaio Corso modulare FONDERIA PER NON FONDITORI (F) – aprile/maggio Corso ADDITIVE METALLURGY (MFM-ML-MP) – marzo / aprile Giornata di Studio LO SVILUPPO TECNOLOGICO DEGLI IMPIANTI DI PRODUZIONE A CALDO DELLE VERGELLE ALTO CARBONIO E ALTO LEGATE E PER FILO SALDANTE (LPM) – marzo/aprile, Lecco c/o Caleotto Giornate di Studio GETTI STRUTTURALI (P) – Brescia, aprile Seminario TRASMISSIONI NELL’AUTOMOTIVE: DALL’ACCIAIERIA AL PROCESSO DI PALLINATURA (TTM) – 16-17 giugno, Modugno (Bari) c/o Magna Corso TRIBOLOGIA INDUSTRIALE (RIV) – 22-23 giugno webinar, 29-30 giugno, Modena Corso MICROSCOPIA ELETTRONICA IN SCANSIONE - SEM - III Edizione (MFM) – giugno Giornata di Studio RACCORDERIA E PRESSATURA. GLI ASPETTI METALLURGICI (LPM) – giugno, Suzzara c/o Intertraco Italia Giornata di Studio TRATTAMENTI PER LA RIMOZIONE DEL PIOMBO PER IL RICICLO DEGLI OTTONI (MTA) – primavera Corso di base SOLIDIFICAZIONE (MFM) –primavera Corso itinerante MACCHINA FUSORIA (A) - primavera / estate Corso MASTER PROGETTAZIONE STAMPI (P) – itinerante, 13 settembre-ottobre-novembre-dicembre FaReTra (Fair Remote Training) - FORMAZIONE E AGGIORNAMENTO A DISTANZA Modalità Asincrona (registrazioni) Giornata di Studio PRESSOCOLATA IN ZAMA Giornata di Studio LA SFIDA DELLA NEUTRALITÀ CARBONICA Corso itinerante METALLURGIA SICURA Corso modulare TRATTAMENTI TERMICI Corso modulare I REFRATTARI E LE LORO APPLICAZIONI Corso GLI ACCIAI INOSSIDABILI 11ª edizione Corso FAILURE ANALYSIS 11a edizione Giornata di Studio PERFORMANCE E DEGRADO DEI MATERIALI METALLICI UTILIZZATI IN CAMPO EOLICO: CAPIRE PER PREVENIRE Giornata di Studio DIFETTI NEI GETTI PRESSOCOLATI: POROSITA’ DA GAS Corso PROVE MECCANICHE Corso di base LEGHE DI ALLUMINIO Giornata di Studio GREEN ECONOMY E ASPETTI AMBIENTALI PER L'INDUSTRIA DEI RIVESTIMENTI Giornata di Studio IL CICLO DI FABBRICAZIONE DI UNA VALVOLA. NORMATIVE, PROGETTO, ACCIAIO, FUCINATURA COLLAUDO Corso CORROSIONE PER NON CORROSIONISTI Giornata di Studio TECNOLOGIE DI FORMATURA DELLE ANIME IN SABBIA PER GETTI IN LEGA LEGGERA

L’elenco completo delle iniziative è disponibile sul sito: www.aimnet.it

(*) In caso non sia possibile svolgere la manifestazione in presenza, la stessa verrà erogata a distanza in modalità webinar

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Atti e notizie - AIM news

RAIDMAP 2021 Relazione finale ad un evaluation board, composto da esperti di estrazione accademica e professionale. L’evaluation board di RAID-

MAP 2021 era composto da Beate Brede (Fraunhofer Insti-

tute – Germania), Roberto Montanari (Università di Roma 2 – Italia), Fabio Ferri (EIT RM, CLC-S – Italia), Ferdinand Bulmer (EIT RM – Germania), Robert Eriksson (Jernkonto-

ret – Svezia), Massimo Malaguti (Consulente – Italia), Lucia

Protopapa (ENEA – Italia), Claudio Testani (APRE – Italia).

Il coordinamento operativo dell’evaluation board è stato effettuato dalla Prof.ssa Lisa Biasetto dell’Università di Padova.

Si è tenuto il 4 e il 5 novembre 2021, presso la sede del Fraunhofer Forum allo SpreePalais di Berlino, l’evento

Nel corso dell’evento finale le idee selezionate sono sta-

MAterials Projects) è un'iniziativa di formazione avanzata,

re attenzione agli aspetti di fattibilità e di budget. Le idee

muovere la collaborazione tra giovani studenti di inge-

ternazionale per verificarne il potenziale a diventare veri e

sviluppo di idee innovative riguardanti progetti di ricerca

EIT – Raw Materials.

tuzione dei materiali. Partner universitari del Progetto

I gruppi selezionati per partecipare all’evento finale

conclusivo di RAIDMAP 2021. RAIDMAP (RAw IDeas for

te ulteriormente sviluppate ed elaborate, con particola-

supportata da EIT – Raw Materials, che consiste nel pro-

progettuali sono state quindi presentate in un contest in-

gneria e professionisti del mondo delle imprese, per lo

propri progetti di ricerca, o startup nell'ambito dei bandi

nel campo dei nuovi materiali e del riciclo e della sostisono la Scuola di Ingegneria dell’Università di Padova,

dell’edizione 2021 sono stati SLAM, ODD-W e FerroSilva.

Norwegian University of Science and Technology (NTNU)

Il Gruppo SLAM (Sustainable Lightweight Automotives

nhofer Institute e il Centro Ricerche Fiat. L’evento finale

re, ha presentato un progetto nel settore dell’automotive

Italiana di Metallurgia.

li più leggeri, attraverso l’impiego di nuovi materiali e di

il Royal Institute of Technology (KTH) di Stoccolma e il

di Trondheim, mentre i referenti tecnologici sono il Frau-

with safe and economic Materials), che è risultato vincito-

è stato organizzato in collaborazione con l’Associazione

per la produzione industriale sostenibile di autoveico-

All’interno del progetto RAIDMAP gli studenti di ingegne-

tecnologie manifatturiere affidabili ed economiche.

ria, i rappresentanti delle imprese (sono state coinvolte le

Gli obiettivi di SLAM, che corrispondono alle sfide affron-

e FerroSilva) e i tutor accademici hanno affrontato proble-

riferimento sostanzialmente alla riduzione del peso delle

eventi opportunamente studiati per far incontrare le idee

carbon footprint del processo industriale e alla ottimizza-

aziende Norsk Hydro, Enginsoft, SINTEF, Boliden Group

tate dal gruppo nella fase di sviluppo del progetto, fanno

mi tecnologici reali, attraverso un percorso che si basa su

parti assemblate, e quindi dei veicoli, alla riduzione del

degli studenti con l’esperienza dei professionisti d’impre-

zione dei parametri di progetto e produzione dei veicoli.

sa, su questioni industriali attuali e su temi come l’economia circolare, il riuso e la sostituzione dei materiali.

Gli studenti seguiti dai tutor accademici e aziendali hanno sviluppato la loro idea progettuale, sottoponendola

La Metallurgia Italiana - November/December 2021

L’evaluation board di RAIDMAP 2021 ha ritenuto il progetto di particolare interesse sia per le ampie e positive rica-

dute in termini di sostenibilità ambientale ed economica

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Atti e notizie - AIM news

dei processi produttivi e del ciclo di vita del prodotto, sia

per la formulazione attenta e chiara di obiettivi, metodi e costi del progetto.

Il Gruppo ODD-W (The On-Demand Digital Wharehouse) ha presentato una soluzione progettuale per l’introduzione della manifattura additiva nella gestione dei pezzi di ricambio di parti e componenti industriali.

I pezzi di ricambio infatti vengono spesso consegnati da punti di riordino che possono essere anche molto lon-

tani dalla destinazione finale, con una logistica spesso

scadente e scarse strutture di stoccaggio. Esiste quindi la necessità di ridurre i costi per il trasporto e lo stoccaggio dei pezzi di ricambio in molti siti produttivi.

Il progetto ODD-W propone una soluzione basata sull’im-

piego della manifattura additiva e di altri metodi dell’industria metallurgica per riparare le parti di ricambio danneggiate, attraverso tecnologie di reprint/repair/resurface.

Le ricadute positive del progetto ODD-W sono ampie e riguardano principalmente, per quanto riguarda diretta-

mente lo stoccaggio, la diminuzione del capitale impiegato per l’immagazzinamento dei pezzi, la minor necessità

di luoghi dedicati allo stoccaggio e del relativo personale,

la riduzione dell’obsolescenza dei pezzi stoccati in cattive condizioni. Si riduce inoltre la footprint carbon per la minore attività di trasporto dei pezzi di ricambio, e il rischio

di costi indotti dovuti al fermo di produzione per mancanza di un pezzo.

La Metallurgia Italiana - Novembre/Dicembre 2021

Il Gruppo FerroSilva ha infine proposto una soluzione per produrre DRI (Direct Reduced Iron) utilizzando biomassa gassificata.

Gli obiettivi di aumento della produzione dell’acciaio, in

considerazione dell’aumento della domanda globale, e di contemporanea riduzione delle emissioni di CO2 sono

attualmente incompatibili senza l’individuazione di nuove soluzioni “green”.

La produzione di DRI utilizzando biomassa gassificata offre l'opportunità di una sensibile riduzione delle emissioni

di CO2. Le industrie siderurgiche di un Paese produttore di acciaio come la Svezia, che ha costituito il contesto di

riferimento di questo progetto, hanno inoltre il vantaggio della disponibilità di grandi quantità di biomassa da resi-

dui forestali, in presenza di un prezzo più alto per il gas naturale.

Il progetto ha una valenza di carattere strategico su scala

europea, e può rivestire un interesse significativo all’in-

terno dei futuri piani si sviluppo sostenibile basati sull’impiego di tecnologie green.

A conclusione dell'evento si sono quindi tenute le premiazioni di tutti i gruppi partecipanti e gli interventi finali

di Franco Bonollo, Presidente della Scuola di Ingegneria

dell'Università di Padova, di Beate Brede del Fraunhofer

Institute, di Ferdinand Bulmer di EIT RawMaterials e di Lars Arnberg, docente del Royal Institute of Technology – KTH.

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Metallurgia 2040 LA METALLURGIA E IL CONTESTO INDUSTRIALE E MANIFATTURIERO ITALIANO È certamente ben noto il ruolo centrale del settore metalmeccanico nell’industria manifatturiera italiana, a cui contribuisce in misura del 47,7% in termini di valore aggiunto. È peraltro molto ben intuibile (a partire da banali considerazioni semantiche) come la Metallurgia giochi un ruolo chiave per l’industria metalmeccanica e manifatturiera, sia in

maniera diretta (produzione di metalli e leghe, con una incidenza del 35,5%) che indiretta (attrezzature e macchinari per numerose filiere produttive). →

Le leghe metalliche sono i materiali strutturali più diffusamente utilizzati nell’Ingegneria, in ragione della pecu-

→

L’inter-settorialità della Metallurgia, e il suo impatto diretto e indiretto sulle varie filiere produttive è ben illu-

→

La produzione italiana di metalli e leghe è essenzialmente basata sui processi di riciclo e rifusione del rottame,

liare combinazione di resistenza, tenacità, costo e sostenibilità ambientale. strato in termini generali nella Fig. 1 [1].

sempre più strategici in un’ottica di economia circolare.

Fig.1 -Ruolo inter-settoriale della metallurgia nelle principali filiere industriali italiane [1].

Tra i materiali metallici essenziali per la produzione industriale, vi sono l’acciaio e le leghe di alluminio. →

L’acciaio ha come principale settore di utilizzo quello delle costruzioni con una quota pari al 36,5%, com-

prensivo delle nuove costruzioni intese sia come investimenti del genio civile che nuove costruzioni private, oltre alle attività di manutenzione. Tra gli altri settori utilizzatori si ritrovano: la meccanica (20,2%), i prodotti in metallo (18,7%), l’automotive (17,1%), gli elettrodomestici (3,2%), gli altri mezzi di trasporto (2,7%) [2]. →

Le leghe di alluminio sono sempre più strategiche nel settore della mobilità (39%), delle costruzioni (24%),

del packaging, alimentare e sanitario (17%), della meccanica ad alto valore aggiunto (13%) e dei beni di consumo (7%), come illustrato in Fig. 2 [3].

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Fig.2 - Utilizzi industriali delle leghe di alluminio.

La metallurgia è anche un attore fondamentale delle sfide globali della trasformazione digitale e della sostenibilità, ambientale ed economica:

→ La digitalizzazione (simulazione, controllo, monitoraggio) dei processi può trovare validazione (e quindi reale implementazione industriale) solo se strettamente connessa alle interazioni tra struttura e proprietà delle leghe metalliche

→ Un settore ad elevatissimo livello di innovazione, come l’Additive Manufacturing, è necessariamente legato alla

disponibilità di materie prime metalliche di elevatissima qualità e alla necessità di una conoscenza metallurgica di base per lo sviluppo e l’ottimizzazione di prodotti e processi (con particolare riguardo allo sviluppo di trattamenti termici e superficiali dedicati).

→ La sostenibilità ambientale e una reale concretizzazione del concetto di economia circolare, fortemente auspicate

dalla comunità internazionale, non possono prescindere dai metalli, sia in termini di produzione di leghe ad elevate prestazioni a partire da rottame (le leghe metalliche sono gli unici materiali che, riciclati, non presentano un decadi-

mento delle loro prestazioni e vengono riutilizzati per le medesime applicazioni), sia in termini di lightweight design,

cioè di progettazione di strutture leggere e resistenti in grado di minimizzare i consumi energetici nel settore della mobilità, sia per quanto attiene all’ottimizzazione dei processi siderurgici e metallurgici (da rendere meno energivori e in grado di ridurre o re-impiegare le scorie generate);

→ La gestione delle terre rare, bene strategico (anche in termini politico-economici) per l’intero settore delle materie prime per le batterie e la mobilità sostenibile, richiede un accresciuto bagaglio di conoscenze sia di metallurgia estrattiva che di processi di recupero e riciclo.

→ Le criticità legate alla disponibilità e alla variabilità di prezzo dei semilavorati rendono necessaria, per le varie tipologie di aziende ed operatori coinvolti, una conoscenza di base dei processi metallurgici di trasformazione.

LA METALLURGIA NEL PIANO NAZIONALE INDUSTRIA 4.0. E NEL PNRR È certamente utile esaminare gli esiti del Piano Nazionale Industria 4.0. Gli investimenti in beni strumentali per la tra-

sformazione digitale delle imprese (strumento dell’iper-ammortamento, Fig. 3) sono stati nell’ordine dei 10 miliardi di

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euro, utilizzati prevalentemente dall’industria manifatturiera. All’interno della manifattura, il settore in cui l’investimento è stato maggiore è quello dei prodotti in metallo (26% del totale degli investimenti iper-ammortizzati) [4].

Fig.3 - Ruolo dell’industria metallurgica nel Piano Nazionale Industria 4.0.

Numerosi sono anche, nel PNRR, gli ambiti in cui la Metallurgia può collocarsi a pieno titolo: -

MISSIONE 1: DIGITALIZZAZIONE, INNOVAZIONE, COMPETITIVITÀ, CULTURA E TURISMO

Digitalizzazione, Innovazione e competitività nel sistema produttivo -

MISSIONE 2: RIVOLUZIONE VERDE E TRANSIZIONE ECOLOGICA

Energia rinnovabile, Idrogeno, Rete e Mobilità sostenibile Efficienza energetica e riqualificazione degli edifici -

MISSIONE 3: INFRASTRUTTURE PER UNA MOBILITÀ SOSTENIBILE

Investimenti sulla rete ferroviaria Intermodalità e logistica integrata -

MISSIONE 4: ISTRUZIONE E RICERCA

Dalla Ricerca all’Impresa È peraltro significativo che nel PNRR l’acciaio venga menzionato un numero di volte confrontabile con quello di “Intelligenza Artificiale” e “Internet of Things”.

GLI SCENARI FUTURI PER LA DIDATTICA IN METALLURGIA Le principali analisi sulle professioni del futuro evidenziano un ruolo sempre più pervasivo, anche nell’industria manifatturiera e metallurgica, dell’Intelligenza Artificiale, dei Big Data e dell’Internet of Things [5]. È chiaro che queste tecnologie contribuiranno fortemente ad ogni futuro sviluppo industriale, ma non può essere sottovalutato il fatto che: →

Serviranno nuovi profili professionali per gestire adeguatamente tali tecnologie,

→

Questi profili dovranno avere un ampio background metallurgico, proprio per garantire un utilizzo cosciente e

consapevole (e non a-critico e ottuso) delle suddette tecnologie.

La formazione universitaria, nel settore metallurgico, è quindi chiamata ad alcune sfide: →

Trasmettere, a tutti i livelli e nei vari contesti, una nuova visione della Metallurgia, sostenibile in termini am-

bientali ed economici, “pulita” e sicura, in grado di implementare l’innovazione digitale e “trasversale” rispetto a qualsiasi produzione industriale.

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→

Sviluppare un modello formativo che anticipi gli sviluppi tecnologici in modo da avere un rapido impatto sul

mondo del lavoro, “costruendo” figure di “esperto di dominio” nel settore metallurgico, in grado di fornire, all’interno di team di lavoro multi-disciplinari e spesso multi-aziendali, competenze e informazioni tecnologicamente focalizzate. →

Potenziare e attualizzare quanto più possibile le esperienze di laboratorio, legandole a case-histories applica-

tive. →

Agire da protagonista nei processi di formazione continua e lifelong learning, che diventeranno sempre più

parte integrante dell’attività lavorativa, sia con iniziative a livello di Master che, soprattutto, mediante percorsi di alta formazione più snelli e mirati rispetto alle esigenze industriali.

Ne consegue che gli insegnamenti di ambito metallurgico dovranno sempre più integrare i concetti basilari della disciplina con le tematiche di maggior attualità e valenza strategica per il futuro. A titolo puramente esemplificativo si possono citare - Produzione sostenibile dell’acciaio e decarbonizzazione dei cicli siderurgici, - Processi sostenibili di riciclo, affinazione, valorizzazione del rottame, - Leghe leggere ad elevate prestazioni, leghe e compositi per applicazioni in condizioni termiche e ambientali estreme, leghe metalliche ad elevate caratteristiche funzionali, leghe metalliche biocompatibili, progettazione e sviluppo di leghe innovative mediante Intelligenza Artificiale, - Tecnologie innovative di manifattura (AM), rivestimenti e processi di modificazione/protezione delle superfici, - Componenti metallici innovativi, multi-funzionali e con sensori integrati, - Modelli predittivi processo-struttura-proprietà, anche basati su sistemi innovativi di elaborazione dei Big Data, - Tecniche avanzate di caratterizzazione.

Non si tratta quindi di e-radicare la disciplina e l’insegnamento della metallurgia tradizionale, quanto piuttosto di effettuare azioni di adeguamento dell’offerta formativa includendo nuove competenze che aderiscano alle sfide globali dell’ingegnere futuro, e alla sua necessità di collocarsi in gruppi di lavoro fortemente inter-disciplinari.

Dal punto di vista accademico, la trasversalità delle discipline metallurgiche dovrà tradursi in una variazione di paradigma. L’attuale collocazione degli insegnamenti metallurgici (lauree triennali in ingegneria industriale e chimica industriale e nelle lauree magistrali in ingegneria chimica, dei materiali, meccanica e in chimica industriale) dovrà entrare a pieno titolo nei corsi di laurea a carattere energetico, ambientale, gestionale, dei trasporti, così come nei nuovi percorsi di laurea ad orientamento professionale.

La Metallurgia dovrà poi avere un ruolo-chiave in molti corsi universitari di nuova concezione. In altre parole, i concetti di trasversalità e inter-disciplinarietà devono tradursi in termini di nuova didattica, più adeguata alle sfide del mondo industriale e più in generale della società, in corsi tenuti congiuntamente da esperti di discipline diverse tra cui la metallurgia (non solo corsi per ingegneri, ma anche destinati all’ambito della medicina, in cui i materiali metallici stanno offrendo soluzioni nemmeno ipotizzabili qualche anno fa). Già oggi, le numerose collaborazioni di ricerca tra docenti universitari del settore metallurgia e l’industria rappresentano un punto di forza dell’offerta formativa, caratterizzata da molte attività didattiche esperienziali (learning by doing). In prospettiva futura, la didattica innovativa dovrebbe prevedere l’integrazione, nei corsi, di contributi di esperti industriali, per consolidare la formazione di figure professionali sempre più vicine al mondo del lavoro.

Non va poi dimenticata la possibilità di ulteriori ambiti formativi legati a tirocini aziendali, in grado sia di far conoscere/ formare dal punto di vista pratico/applicativo lo studente, sia di innescare/potenziare il dialogo tra Industria e Accademia. Questo aspetto è cruciale nella formazione di un ingegnere “esperto di dominio metallurgico”.

La variazione di paradigma appena individuata non può che svilupparsi di concerto con il mondo industriale. In que-

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sto senso, va sottolineato che la docenza delle discipline metallurgiche, strutturata nel SSD ING-IND/21, costituisce probabilmente un caso unico di interazione e integrazione con il mondo industriale. Pressoché la totalità dei docenti ING-IND/21 aderisce infatti all'AIM (Associazione Italiana di Metallurgia), fondata nel gennaio 1946, ente culturale, senza fini di lucro, mirato alla diffusione della scienza e della tecnologia dei materiali metallici e di altri materiali per l'ingegneria. Con oltre 2000 soci industriali e un centinaio di associati universitari, AIM rappresenta l’intera comunità accademica e industriale nell’ambito metallurgico. Le attività dell’AIM si articolano in circa 20 centri di Studio tematici in cui la presenza di docenti universitari ed esperti industriali è fortemente integrata. Il Settore ING-IND/21 è ufficialmente costituito nel Coordinamento della Ricerca e della Didattica Universitaria in Metallurgia (COMET), come parte integrante di AIM. L’integrazione tra SSD ING-IND/21 e AIM ha già permesso, da molti anni, di trovare concrete occasioni di confronto tra mondo produttivo e didattica universitaria, offrendo anche numerose e ben documentate iniziative di lifelong learning.

RIFERIMENTI BIBLIOGRAFICI [1]

Rapporto Annuale 2019, ISTAT)

[2]

Federacciai: Il settore siderurgico: impatto emergenza Covid-19 e misure urgenti per il rilancio (2020)

[3]

European Aluminium Association, https://www.european-aluminium.eu/

[4]

Rapporto Centro Studi Confindustria (2019)

[5]

The Future of Jobs Report 2020, World Economic Forum (2020)

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Comitati tecnici / Study groups CT PRESSOCOLATA (P)

(riunione telematica del 28 settembre 2021) Notizie dal Comitato •

Il CT accoglie un nuovo membro, tecnico metallurgista del settore acciaio.

•

Il consueto giro di tavolo tra i presenti sulla situazione del mercato evidenzia i problemi relativi al costo delle materie prime (gas ed energia elettrica). Il mercato automotive si presenta in maniera disomogenea.

Consuntivo attività svolte •

Il presidente Parona esprime il suo rammarico per l’annullamento della GdS “Eco-sostenibilità: una sfida per i getti pressocolati”, già prevista per il 22 settembre 2021. Nonostante il tema sia di attualità e di grande interesse, come confermano molti dei presenti, il numero di iscritti era insufficiente per dare il via alla manifestazione. Si cerca ora di raccogliere informazioni e dettagli per poter riprogrammare l’evento in maniera più attraente.

Manifestazioni in corso di organizzazione •

La GdS “Zama HPDC 2021” – coordinatori Pola e Valente – è confermata in modalità webinar per il 6 e 7 ottobre 2021. I coordinatori invieranno a breve il programma per preparare la locandina.

•

Il corso “Getti Strutturali” – coordinatori Pola e Valente – viene ridefinito in modalità ibrida in due giornate complete per il 3 e 4 novembre 2021. I relatori saranno tutti in presenza. Si discute di alcuni dettagli delle tempistiche

Iniziative future •

La “pillola” dedicata alla difettologia sui getti pressocolati per giunzioni fredde e metallizzazioni sarà definita nel corso della prossima riunione.

•

Il presidente Parona propone per il 2022 una GdS dedicata ai progettisti in generale partendo dalla fase di CO-DESIGN per avere come obiettivo un prodotto adatto alla tecnologia di pressocolata.

CT AMBIENTE E SICUREZZA (AS) (riunione telematica del 14 ottobre 2021)

Notizie dal Comitato •

Un nuovo membro viene accettato nel Comitato; è responsabile del settore Ambiente e sicurezza di una acciaieria ed interessato a condividere le sue esperienze con gli altri membri del CT.

•

Come sempre, i membri del CT si scambiano informazioni circa esperienze o insegnamenti che possano essere utili. Sono stati presentati alcuni incidenti o mancati incidenti e si è discusso dell’importanza fondamentale che tutte le procedure siano precise e complete, che ci siano i DPI e che informazione, formazione e addestramento siano evidenti e registrati.

•

Si discute anche delle misure prese nelle aziende in rapporto alla recente introduzione di controlli siui green-pass, soprattutto per trasportatori esteri.

Consuntivo di attività svolte •

Si è concluso il corso itinerante “Metallurgia Sicura” che si è svolto in settembre 2021 presso Beltrame, Feralpi e Cogne con grande partecipazione. L’augurio è che, in futuro, altri stabilimenti aprano le loro porte a queste manifestazioni. La presenza registrata è stata di circa 55-75 persone a giornata. Il gradimento, sui questionari compilati dai partecipanti, è stato da molto buono a ottimo, soprattutto per l’opportunità di poter visitare un altro stabilimento e confrontarsi su temi comuni.

Iniziative future Sicurezza •

Due temi interessanti, gia citati, sono relativi al lavoro in spazi confinati e alla radioprotezione, che saranno valutati al prossimo incontro.

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Ambiente •

Direttiva regionale su scorie nere: il tema è interessante e si forma un gruppo di lavoro per portare una bozza di programma al prossimo incontro e trovare una azienda ospitante.

•

Molte altre tematiche vengono citate dai presenti: idrogeno e rinnovabili, biochar e polimeri.

CT ACCIAIERIA (A) CT FORGIATURA (F)

(riunione telematica congiunta del 10 settembre 2021)

Notizie dal Comitato •

I presenti danno il benvenuto a Daniele Giunta, di RHI, che entra a far parte del comitato.

Consuntivo di attività svolte •

Mapelli, presidente del CT Acciaieria, informa che il webinar FaReTra su “Carbon Neutrality” ha ottenuto un riscontro positivo sia in termini di iscrizioni (un’ottantina di partecipanti) che di apprezzamento, come risulta dall’analisi dei questionari di soddisfazione.

Manifestazioni in corso di organizzazione •

Il Corso di aggiornamento “Refrattari siderurgici e loro applicazioni” avrà luogo tra la fine di settembre e l’inizio di ottobre, in modalità webinar su 6 giornate da circa 3 ore ciascuna. Sono già state raccolte di diverse iscrizioni.

•

Rampinini, presidente del CT Forgiatura, presenta il programma della GdS “Il ciclo di fabbricazione di una valvola: normative, progetto, acciaio, fucinatura, collaudo”, che si terrà in presenza l’11 novembre presso il KilometroRosso vicino a Bergamo.

•

Rampinini conferma l’intenzione di organizzare la GdS “ITER experience for new DTT Enea Fusion Reactor” in presenza, possibilmente in Francia, nel periodo maggio/giugno 2922.

CT METALLI LEGGERI (ML)

(riunione telematica del 15 ottobre 2021) Manifestazioni in corso di organizzazione •

La GdS “Tecnologia di formatura anime in sabbia per getti in lega leggera” – coordinatori Amalberto e Spaccasassi – si terrà il 2-3 dicembre, presso il Kilometro Rosso (BG) in modalità duale (in presenza e virtuale). Tutti i relatori ed il programma sono confermati.

•

Il corso di base “Leghe di Alluminio” si terrà in 16 e 17 novembre in modalità webinar, coordinatori Morri e Fracchia. Ci sono già diversi iscritti che potrebbero aumentare. Il programma prevede alcune modifiche rispetto alle edizioni precedenti.

Iniziative future •

Il coordinatore Garagnani non ha potuto finalizzare l’organizzazione della GdS “L’alluminio nell’automobile – La storia incontra il futuro”, in memoria dell’ing. Giorgio Valentini. Se ne riparlerà alla prossima riunione per organizzarla in maggio-giugno 2022.

•

Il tema dell’estetica e i trattamenti superficiali” potrebbe essere trattato in una giornata con programma da definire, di cui si discuterà nelle prossime riunione.

CT METALLURGIA DELLE POLVERI E TECNOLOGIE ADDITIVE (MP) (riunione telematica congiunta del 09 settembre 2021)

Notizie dal Comitato •

La Presidente Rampin dà il benvenuto alla dr.ssa Lavina Tonelli, ricercatrice presso l’Università di Bologna, che entra a far parte del CT e al dr. Giorgio Valsecchi, che sostituisce il dr. Gionda come rappresentante di TAV Vacuum Furnaces all’interno del CT.

La Metallurgia Italiana - November/December 2021

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Manifestazioni in corso di organizzazione •

La Presidente Rampin informa con rammarico che la GdS “Press & Sinter”, prevista come webinar il 10 giugno 2021, è stata sospesa per mancato numero minimo di iscritti. Si discute delle possibili cause di questo insuccesso e si decide di riprovare a realizzare l’evento in presenza intorno a marzo-aprile 2022.

Iniziative future •

La terza edizione del Corso “Additive Metallurgy” (coordinatori Molinari-Casati) organizzato in collaborazione con altri due Centri di Studio, già prevista per settembre/ottobre 2021, è stata spostata al 2022 perché i coordinatori dei tre CT propendono per una erogazione in presenza..

•

La GdS “Materiali per alta temperatura” è stata nuovamente rimandata per poter tenere la manifestazione in presenza, a partire da marzo 2022.

•

Il doppio seminario organizzato con il CT Trattamenti Termici e Metallografia viene ugualmente spostato al 2022

CENTRO RIVESTIMENTI E TRIBOLOGIA (R) (riunione del 23 novembre 2021)

Notizie dal Comitato •

Il Presidente Bolelli presenta Giacomo Falanga di Modena Centro Prove, che viene accolto dal comitato come membro effettivo a partire dalla prossima riunione.

Consuntivo di attività svolte •

La GdS webinar “Green economy e aspetti ambientali per l’industria dei rivestimenti” del 17/11/2021 ha raccolto poche iscrizioni ma i partecipanti hanno espresso un giudizio positivo.

Manifestazioni in corso di organizzazione •

La prossima edizione del corso di ”Tribologia” è prevista per la seconda metà di giugno 2022. Diversi membri presenti confermano la loro disponibilità per le presentazioni, altri devono dare conferma. Nella precedente edizione il corso si era svolto in diverse sedi, per cui c’era spazio per le visite; molto probabilmente il corso si terrà in una sola sede e quindi c’è possibilità di inserire altri interventi, su cui si discute. Si discute anche della sede: Bassani consiglia di fare due mezze giornate consecutive se la sede rimane la stessa, e di fare una terza giornata in modalità webinar (eventualmente suddivisa in due mezze giornate), in modo da facilitare la partecipazione delle aziende ed evitare il doppio viaggio. Dopo aver discusso dei dettagli, si ipotizzano date verso la fine di giugno 2022 nella sede di Modena.

CT CORROSIONE (C)

(riunione telematica del 09 luglio 2021) Notizie dal Comitato •

Sabina Grassini del Politecnico di Torino entra da oggi a far parte del CT C.

Manifestazioni in corso di organizzazione •

Il corso di “Corrosione per non corrosionisti” in collaborazione con il CT Controllo e Caratterizzazione Prodotti è previsto per il 24 e 25 novembre 2021. Bolzoni, coordinatore per il CT C, ha definito gli ultimi dettagli ma bisognerà attendere gli ultimi giorni per sapere se la manifestazione si potrà tenere in presenza.

•

La GdS “Ruolo dei materiali nell’economia dell’idrogeno” è confermata per il 27 gennaio 2022 ed è organizzata in cooperazione con i CT Metallurgia Fisica e Scienza dei Materiali e Materiali per l’Energia. Cabrini, coordinatrice per il CT C insieme a Bolzoni, illustra il programma e il carattere degli interventi. Mancano ancora alcuni dettagli.

Iniziative future •

La 15° edizione delle “Giornate Nazionali sulla Corrosione e Protezione” si svolgerà nel 2023 presso il Politecnico di Torino, non avendo potuto effettuare in tale sede la manifestazione nel 2021. Si discute su modalità e tempistiche per la ricezione delle me-

La Metallurgia Italiana - Novembre/Dicembre 2021

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morie e sulla scelta dei coordinatori di sessione.

•

Bellezze e Balbo riferiscono sulla bozza di programma per un corso/scuola sull’elettrochimica del processo di corrosione e sulle relative tecniche elettrochimiche di misura. Balbo illustra i possibili titoli per l’iniziativa e gli argomenti da trattare. L’impostazione appare di natura accademico-teorica perché l’iniziativa era stata originariamente pensata per dottorandi e ricercatori. Ad alcuni il programma appare poco adeguato a un tecnico di laboratorio di un’azienda. Per questo si valuterà la possibilità di due iniziative, una più teorica (una scuola di dottorato, il cui programma è a grandi linee definito) e una più pratica rivolta ai tecnici delle aziende.

CT AIM/ASSOFOND - FONDERIA (F) (riunione telematica del 17 novembre 2021)

Manifestazioni in corso di organizzazione •

Il CT lavora per la messa a punto del primo modulo del corso “Fonderia per non fonditori”: sono previste 23 lezioni da un’ora affidate a figure accademiche e professionali. La organizzazione e la gestione del corso saranno affidate ad AIM; si prevede un test a fine corso per ottenere sia l’attestato di partecipazione che alcuni crediti formativi. Il corso si potrebbe tenere in aprile/maggio 2022.

Iniziative future •

Bonollo, coordinatore del corso di “Metallografia delle ghise”, conferma che la programmazione è già ad un punto avanzato e il corso potrebbe partire da febbraio 2021.

CT CONTROLLO E CARATTERIZZAZIONE PRODOTTI (CCP) (riunione telematica del 01 ottobre 2021)

Consuntivo di attività svolte •

Il video di “Pillole di prove meccaniche” preparato da Trentini e pubblicato sul canale social di AIM ha avuto poche visualizzazioni. Si decide quindi di sospendere la preparazione di ulteriori pillole per concentrarsi sugli altri eventi, in particolare sul video di visita al laboratorio per il corso di prove meccaniche.

Manifestazioni in corso di organizzazione •

Il corso “Prove meccaniche” (26-27 ottobre e 9-10 novembre 2021) era pensato in modalità mista, ma la grande maggioranza degli iscritti preferisce la fruizione in remoto. Si attenderanno gli ultimi giorni utili per definire cosa fare, tenendo conto anche della capienza della sala riunioni AIM. La maggioranza degli iscritti fino a questo momento ha chiesto di iscriversi ad entrambi i moduli.

Durante la discussione sono stati definiti gli ultimi dettagli delle lezioni e dei docenti.

•

Corso “Corrosione per non corrosionisti”: il presidente Toldo annuncia che è stato definito con Bolzoni (del CT Corrosione) il programma definitivo e mostra ai presenti la locandina. Quasi tutte le presentazioni del CT CCP sono già pervenute e appaiono interessanti. Il corso è confermato per il 24 e 25 novembre in modalità mista.

Iniziative future •

La GdS sulla “Microscopia elettronica applicata alla failure analysis” si potrà organizzare solo dopo il corso organizzato in presenza dal CT Metallurgia Fisica, quindi occorre aspettare. L’impostazione della giornata sarà simile alla precedente, ma ovviamente i relatori presenteranno esempi differenti.

•

La GdS “Caratterizzazione dei materiali da Additive Manufacturing” – coordinatrice Bisaglia – resta al momento in attesa di definizione.

La Metallurgia Italiana - November/December 2021

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Normativa / Standards UNI EN 10222-2:2017

Norme pubblicate e progetti in inchiesta (aggiornamento 30 novembre 2021)

Fucinati

di

acciaio

— Specific requirements for offshore per

apparecchi

a

pressione - Parte 2: Acciai ferritici e ISO/TS 18683:2021

martensitici aventi caratteristiche

Guidelines for safety and risk assessment

Norme UNSIDER pubblicate da UNI nei mesi di ottobre e novembre 2021

UNI EN 10253-2:2008

of LNG fuel bunkering operations

- Parte 2: Acciai non legati e acciai ferritici

ISO/TS 9516-4:2021

Raccordi per tubazioni da saldare di testa legati con requisiti specifici di controllo

Raccordi a saldare per l'industria alimentare e chimica - Connessioni a T, curve e riduzioni per saldatura

Raccordi per tubazioni da saldare di testa - Parte 2: Acciai non legati e acciai ferritici legati con requisiti specifici di controllo EC 1-2021 UNI EN 448:2019

teleriscaldamento

-

Sistemi

interrate direttamente - Raccordi realizzati in fabbrica con tubi di servizio in acciaio, isolamento termico in poliuretano e guaina esterna in polietilene

Fucinati

di

acciaio

apparecchi

a

fine con elevato limite di elasticità

Fucinati

di

pressione e

acciaio

-

Parte

martensitici

method using fusion preparation method ISO 6368:2021 Petroleum,

2:

aventi

and

natural

components for the evacuation of water

for axial, centrifugal, and rotary screw

from works - characteristics and test

compressors and expanders

pipe

systems

and

EN 13480-5:2017/A2:2021

Progetti UNSIDER messi allo studio

and testing

dicembre 2021

Metallic industrial piping - Part 5: Inspection

EN 13480-2:2017/A8:2021

Metallic industrial piping - Part 2: Materials)

dal CEN (Stage 10.99) – novembre e

prEN ISO 19901-3 rev Petroleum

Refractory of

natural

gas

requirements

for

industries offshore

structures - Part 3: Topsides structure

products

compressive

Specific

and

—

Determination

strength

at

elevated

temperature

prEN 14870-2 rev

Petroleum and natural gas industries — Induction bends, fittings and flanges for

apparecchi Acciai

petrochemical

gas industries — Dry gas sealing systems

iron

ISO 7788:2021 per

fluorescence

spectrometry — Part 4: Performance-based

per

X-ray

their

Cast

ISO 22685:2021

pressione - Parte 4: Acciai saldabili a grano

UNI EN 10222-2:2021

e ISO nei mesi di ottobre 2021

by

methods

bloccati monotubo per reti di acqua calda

UNI EN 10222-4:2021

Norme UNSIDER pubblicate da CEN

EN 877:2021

UNI EN 10253-2:2021

per

Iron ores — Determination of various elements

UNI EN 10374:2021

Tubi

structures — Part 5: Weight management

a

ferritici

caratteristiche

specifiche a temperatura elevata

pipeline transportation systems — Part 2:

Steel — Surface finish of hot-rolled plates

Fittings (ISO 15590-2:2021 modified)

and wide flats — Delivery requirements prEN ISO 4545-1 rev

ISO 4695:2021

Metallic materials - Knoop hardness test -

Iron ores for blast furnace feedstocks —

Part 1: Test method

Determination of the reducibility by the

Norme UNSIDER ritirate da UNI nei mesi di ottobre e novembre 2021 UNI EN 10222-4:2017 Fucinati

di

acciaio

rate of reduction index

prEN ISO 6506-1 rev

Metallic materials - Brinell hardness test ISO 21052:2021

Part 1: Test method (ISO 6506-1:2014)

pipelines — Calculation rules for lengths to

prEN ISO 6506-2 rev

Restrained joint systems for ductile iron per

apparecchi

a

pressione - Parte 4: Acciai saldabili a grano fine con elevato limite di elasticità

be restrained

Metallic materials - Brinell hardness test Part 2: Verification and calibration of testing

ISO 19901-5:2021 Petroleum

La Metallurgia Italiana - Novembre/Dicembre 2021

and

machines (ISO 6506-2:2017) natural

gas

industries

pagina 102

Atti e notizie - AIM news

silicon carbide, total and free silica and

prEN ISO 6506-3 rev

Metallic materials - Brinell hardness test -

total and free silicon

Part 3: Calibration of reference blocks (ISO

prEN ISO 4943

prEN ISO 21068-3 rev

6506-3:2014)

and calculation

Steel and cast iron - Determination of

Chemical analysis of raw materials and

copper content - Flame atomic absorption

prEN ISO 6507-1 rev

refractory

spectrometric method (ISO/DIS 4943:2021)

Metallic materials - Vickers hardness test -

carbide, silicon nitride, silicon oxynitride

Part 1: Test method (ISO 6507-1:2018)

and sialon - Part 3: Determination of

products

containing

silicon

nitrogen, oxygen and metallic and oxidic prEN ISO 6508-2 rev

constituents

test - Part 2: Verification and calibration of

ISO/DIS

–

internazionali

progetti

di

norma

Metallic materials - Rockwell hardness prEN ISO 20182 rev

ISO/DIS 24139-1

testing machines and indenters (ISO 6508-

Refractory test-piece preparation - Gunning

Petroleum and natural gas industries —

2:2015)

refractory panels by the pneumatic-nozzle

Corrosion resistant alloy clad bends and

mixing type guns

fittings for pipeline transportation system — Part 1: Clad bends

prEN ISO 6508-3 rev

Metallic materials - Rockwell hardness test

prEN 10209 rev

ISO/DIS 7992

- Part 3: Calibration of reference blocks

Cold rolled low carbon steel flat products

(ISO 6508-3:2015)

for vitreous enamelling - Technical delivery

Iron ores for blast furnace feedstocks —

conditions

Determination of reduction under load

EN 10025-6:2019/prA1

prEN 10359 rev

ISO/DIS 4943

Part 6: Technical delivery conditions for flat

Laser welded tailored blanks - Technical

Steel and cast iron — Determination of

products of high yield strength structural

delivery conditions

copper content — Flame atomic absorption

Hot rolled products of structural steels -

spectrometric method

steels in the quenched and tempered prEN 10021 rev

condition

General technical delivery conditions for EN 10025-4:2019/prA1

steel products

Part 4: Technical delivery conditions for

prEN 10168 rev

ISO/DIS 4698

Iron ore pellets for blast furnace feedstocks — Determination of the free-swelling index

Hot rolled products of structural steels thermomechanical rolled weldable fine

Steel products - Inspection documents -

grain structural steels

List of information and description

ISO/DIS 24139-1

Petroleum and natural gas industries — Corrosion resistant alloy clad bends and fittings for pipeline transportation system

EN 1092-1:2018/prA1

prEN 10204 rev

Flanges and their joints - Circular flanges

Metallic products - Types of inspection

for pipes, valves, fittings and accessories,

documents ISO/DIS 15589-2

PN designated - Part 1: Steel flanges prEN ISO 21068-1 rev

Chemical analysis of raw materials and refractory

products

containing

silicon

carbide, silicon nitride, silicon oxynitride and sialon - Part 1: General information and sample preparation

Progetti UNSIDER in inchiesta prEN e ISO/DIS – novembre e dicembre 2021 prEN – progetti di norma europei

prEN ISO 21068-2 rev

-

Specific

and

natural

gas

requirements

for

industries offshore

Chemical analysis of raw materials and

structures - Part 10: Marine geophysical

refractory

investigations (ISO 19901-10:2021)

containing

silicon

on ignition, total carbon, free carbon and

petrochemical

and

natural

gas industries — Cathodic protection of pipeline transportation systems — Part 2: Offshore pipelines ISO/DIS 14284

of samples for the determination of chemical composition ISO/DIS 13703-2

Petroleum, petrochemical and natural gas

carbide, silicon nitride, silicon oxynitride and sialon - Part 2: Determination of loss

Petroleum,

Steel and iron — Sampling and preparation

prEN ISO 19901-10 Petroleum

products

— Part 1: Clad bends

EN 13480-3:2017/prA5:2021 Metallic industrial piping - Part 3: Design

La Metallurgia Italiana - November/December 2021

industries — Piping systems on offshore platforms and onshore plants — Part 2:

pagina 103

Atti e notizie - AIM news Materials

ISO/FDIS 683-3 Heat-treatable steels, alloy steels and freecutting steels — Part 3: Case-hardening

ISO/DIS 4943

steels

Steel and cast iron — Determination of copper content — Flame atomic absorption spectrometric method ISO/DIS 4698

Iron ore pellets for blast furnace feedstocks — Determination of the free-swelling index

Progetti UNSIDER al voto FprEN e

ISO/FDIS – novembre e dicembre 2021

FprEN – progetti di norma europei FprEN ISO 10113 Metallic materials - Sheet and strip Determination of plastic strain ratio (ISO/ FDIS 10113:2019) FprEN ISO 683-3 Heat-treatable steels, alloy steels and freecutting steels - Part 3: Case-hardening steels (ISO/FDIS 683-3:2021) FprEN 10202 Cold reduced tinmill products - Electrolytic tinplate

and

electrolytic

chromium/

chromium oxide coated steel

ISO/FDIS

–

internazionali

progetti

di

norma

ISO/FDIS 23296 Metallic materials – Fatigue testing – Force controlled

thermo-mechanical

fatigue

testing method ISO/FDIS 18338 Metallic materials — Torsion test at room temperature ISO/FDIS 1352 Metallic materials — Torque-controlled fatigue testing

La Metallurgia Italiana - Novembre/Dicembre 2021

pagina 104

Centri di Studio CORROSIONE METALLURGIA FISICA E SCIENZA DEI MATERIALI MATERIALI PER L’ENERGIA

27 gennaio 2022

Giornata di Studio

Il ruolo dei materiali nell’economia dell’idrogeno

L

o sviluppo dell’economia dell’idrogeno è fortemente voluto sia a livello europeo sia italiano.

Considerando l’importanza strategica dell’idrogeno, ma anche i costi di investimento nel settore e la necessità di garantirne l’utilizzo nella massima sicurezza, la strategia vincente è sicuramente la cooperazione tra industria, istituti di ricerca ed Università.

La finalità principale di questa Giornata di Studio è fornire un momento di comunicazione tra queste parti, allo scopo di capire meglio il problema, conoscere le relative competenze e creare network per affrontare le affascinanti sfide della transizione energetica.

La Giornata di Studio è focalizzata sulla compatibilità tra l’idrogeno e i materiali destinati alla sua produzione, compressione, trasporto, stoccaggio e utilizzo, partendo dagli aspetti meccanicistici, passando dalle applicazioni per finire con la legislazione attuale.

Sono previsti interventi da parte di docenti universitari e ricercatori, unitamente ai rappresentanti di importanti industrie nel settore, allo scopo di illustrare le loro esperienze e condividere le conoscenze.

Coordinatori: Paola Bassani, Fabio Bolzoni, Marina Cabrini, Giorgio Gavelli

Programma 8.40 Registrazione dei partecipanti in presenza 9.00

Saluti di benvenuto e introduzione

9.30

Le sfide nella gestione dell’idrogeno Marcello Baricco - Università di Torino

10.10 Materiali per la produzione di idrogeno Vladimiro Dal Santo - SCITEC-CNR, Milano 10.50 Intervallo 11.20 Diffusione e infragilimento da idrogeno: aspetti teorici Fabio Bolzoni - Politecnico di Milano Marina Cabrini - Università di Bergamo 12.00 Materiali per serbatoi di stoccaggio e distribuzione in tubazione di idrogeno Alberto Budi - Siad 12.30 Pranzo 13.45 Trasporto dell’idrogeno in tubazioni: normativa e testing Luca Bacchi - Snam 14.15 Materiali polimerici per reti a bassa pressione e tenute Roberto Frassine, Claudia Marano - Politecnico di Milano 14.45 Requisiti normativi (ASME B31.12) per pipelines nuovi ed esistenti per trasporto idrogeno Mario Celant, Francesco Cotzia - Pipe Team 15.15 Intervallo

27 gennaio 2022 h. 8.40 > 17.00

In presenza:

Milano . Centro Congressi Fast Piazzale Rodolfo Morandi 2 Da remoto:

su piattaforma Zoom Segreteria organizzativa

Associazione Italiana di Metallurgia t. +39 02 76021132 +39 02 76397770 info@aimnet.it www.aimnet.it Evento patrocinato da

ASSOCIAZIONE PER LA PROTEZIONE DELLE CORROSIONI ELETTROLITICHE

15.30 Tecniche innovative per la caratterizzazione del comportamento degli acciai in presenza di idrogeno gassoso e sue miscele R. Valentini - Università di Pisa S. Corsinovi, M. Villa - Letomec 16.00 Impiego dell’idrogeno come combustibile nelle turbine a gas per la produzione di energia Carlo Piana, Paola Guarnone - Ansaldo Energia 16.30 Dal metano all’idrogeno: sfide tecnologiche per una combustione green Simone Losa, Andrea Baio – ESA 17.00 Termine

Atti e notizie - AIM news

Indice analitico / Analytic index ACCIAI AD ALTA RESISTENZA / HIGH STRENGTH STEELS

Effetto di affinante e modificante sulla microstruttura delle

modello di trasformazione dell’austenite per le linee di ricottura

E. Fracchia, M. Rosso

Acciai ad alta resistenza per il settore automotive: un semplice continua e zincatura n.9 pag.48

leghe Al-Si da colata n.1 pag.13

V. Colla, R. Valentini, L. Bacchi

Approccio innovativo basato sull’analisi dell’incrudimento di

ACCIAI AD ALTO SILICO / HIGH SILICON STEELS

lega di Al pressocolata n.1 pag.22

Studio dell’evoluzione microstrutturale e delle caratteristiche meccaniche di acciai ad alto silicio austemperati n.6 pag.16

curve di flusso in trazione per qualificare la difettosità di una di G. Angella, G. Timelli, F. Bonollo

M. Franceschi, L. Pezzato, C. Gennari, K. Brunelli, M. Dabalà

Effetti della presenza di impurezze di Sn nella lega AA8006

ACCIAI DA UTENSILI / TOOL STEEL

P. Rossi, A. Leonelli, C. Sinagra, F. Bravaccino, T. Monetta, A.

Alternative alloying concepts of hot work tool steels for application in die casting n.11-12 pag.37

n.1 pag.31 Acquesta

P. Niederhofer, F. van Soest, M. Gürcan, H.-G. Krull, T. Schneiders

Effect of the Cassie Baxter-Wenzel behaviour transitions on the

CS1 - The new hot-work tool steel for die casting dies with the

n.3 pag.15

highest surface requirements n.11-12 pag.43 E. Meurisse, I. Schruff AM process simulation to optimise diecasting tooling n.11-12 pag.49

corrosion performances of AA6082 bsuperhydrophobic surfaces A. Khaskhoussi, L. Calabrese, E. Proverbio Anodizzazione e processi post-anodizzazione per l’aumento della resistenza alla corrosione di leghe dell’Alluminio n.3 pag.22

N. Gramegna, D. Boscolo, G. Scarpa, N. Nardo, F. Bonollo

Zaffora, F. Di Franco, M. Santamaria

ACCIAI INOSSIDABILI DUPLEX / DUPLEX STAINLESS

Caratterizzazione elettrochimica di trattamenti di conversione

Trattamenti elettropulsati su acciaio inossidabile duplex UNS

T. Monetta, A. Acquesta, C. Sinagra, F. Bravaccino, A.W. Ipock

STEELS

S32750 n.9 pag.15 C. Gennari, L. Pezzato, G. Tarabotti, R. Gobbo, M. Forzan,

superficiale Cr-free no-rinse per la lega AA8006 n.3 pag.38

Studio della resistenza a corrosione di laminati in lega AA3005

E. Simonetto, V. Stolyarov, I. Calliari

sottoposti a trattamenti di fosfocromatazione "rinse" e "no-

ACCIAI MAGNETICI / MAGNETIC STEEL

A.W. Ipock, F. Bravaccino, C. Sinagra, T. Monetta, A. Acquesta

attraverso tecniche di Manifattura Additiva n.2 pag.50

ALLUMINIO E SUE LEGHE / ALUMINUM AND ITS ALLOYS

Studio di fattibilità della fabbricazione di nuclei ferromagnetici G. Stornelli, M.R. Ridolfi, P. Folgarait, J. De Nisi, D. Corapi, C. Repitsch, A. Di Schino

ACCIAI MARTENSITICI / MARTENSITIC STEELS

Studio della segregazione di Cr in acciai martensitici tramite analisi XPS n.9 pag.08

rinse" n.3 pag.44

Superfici superidrofobiche biomimetiche su lega di alluminio 6082 con migliorata resistenza alla corrosione n.10 pag.40 A. Khaskhoussi, L. Calabrese, E. Proverbio Residual stress analysis applied to HPDC aluminium components: a case study n.11-12 pag.54

E. Bolli, A. Fava, S. Kaciulis, A. Mezzi, R. Montanari, A. Varone

E. Fracchia, F.S. Gobber, M. Rosso, Y. Kobayashi, C. Mus

ALLUMINIO E LEGHE DI ALLUMINIO / ALUMINIUM

Evaluation of fracture toughness in HPDC aluminum alloys to

Analisi della shell zone di placche in leghe di alluminio ottenute

Tarhouni, D. Frómeta, A. Lara, S. Parareda, I. Tarhouni, D. Casellas

AND ALUMINIUM ALLOYS

mediante colata semi continua n.1 pag.6 A. Leonelli, C. Sinagra, F. Bravaccino, T. Monetta, A. Acquesta

estimate crashworthiness in Automotive parts n.11-12 pag.60

Effects of bismuth on the characteristics of eutectic Si particles in Na-modified A356 alloys n.11-12 pag.73 Ö. Gürsoy, G. Timelli

La Metallurgia Italiana - Novembre/Dicembre 2021

pagina 106

Atti e notizie - AIM news

ANALISI DEI CEDIMENTI / FAILURE ANALYSIS

CORROSIONE SOTTO SFORZO / STRESS CORROSION

P. Cerchier, E. R. Dal Piaz, L. Pezzato, A. Zambon, M. Dabalà,

per precipitazione saldata tramite friction stir welding n.3 pag.6

I. Calliari

M. Cabrini, S. Lorenzi, C. Testa, N. Galizzi, F. Carugo, S. Bocchi, G.

Failure analysis di ruote dentate n.5 pag.6

ARCHEOMETALLURGIA / ARCHEOMETALLURGY

Analisi metallurgica di due spade rinascimentali n.7-8 pag.52 P. Matteis, G. Scavino

Corrosione sotto sforzo di una lega di alluminio-rame indurente

D’Urso, C. Giardini, T. Pastore

FONDERIA / FOUNDRY

Nuova serie Cerabeads CB-ES: la sabbia speciale ad elevata stabilità ter-mica per ridurre l’aggiunta di legante nei processi

Caratterizzazione di manufatti in ferro di epoca fenicio-punica

di formatura Cold-Box, Croning e Inorganico in Fonderia

mediante spettroscopia Raman n.10 pag.08

n.1 pag.37

A. Vietti, N. Donato, E. Angelini, S. Grassini

F. Lepretti - HA Italia

Comportamento elettrochimico di bronzi archeologici arseni-

LAVORABILITA’ ALL’UTENSILE / MACHINABILITY

cali in funzione della concentrazione dell'arsenico in lega

Elettroerosione a filo / Wire EDM

n.10 pag.13

Comparative Machining characteristics studies on SS 304 using

A.Salanitro, G. Ghiara, S. Trasatti, M. Moedlinger

coated and uncoated brass wire through Wire EDM pag.32 T. Suresh, K. Jayakumar, G. Selvakumar, S. Ramprakash

Intervento di ispezione sulle strutture metalliche del Ponte sul fiume Po “Della Gerola” n.10 pag.18 M. Carsana, M. Gastaldi, F. Lollini, E. Redaelli

CARATTERIZZAZIONE MATERIALI /

CHARACTERIZATION OF MATERIALS

Role of high-temperature Equal-Channel Angular Pressing strain path on secondary-phase precipitation in a T6-Al-Cu-LiMg-Ag-Zr-Sc alloy n.7-8 pag.29 M. Cabibbo, S. Acierno, C. Paoletti

LEGHE LEGGERE / LIGHT ALLOYS

Effect of Li addition on mechanical properties of Al-Si-Mg alloy n.11-12 pag.19 O. Özaydin, A.Y. Kaya, E. Armakan Temperature and microstructural-condition dependence for thermal diffusivity and electrical conductivity of a casting AlSi-Cu-Mg alloy n.11-12 pag.67 R. Wang, M.C. Poletti, B. Stauder, R. Fernández Gutiérrez, C. Confalonieri, E. Gariboldi

Characterization of microstructural and mechanical properties of high-pressure die-cast EN AC 46000 alloy n.11-12 pag.31 M. Tocci, L. Montesano, A. Pola, S. Ferri

CORROSIONE IN FESSURA / CREVICE CORROSION

Studio dei fenomeni di corrosione in fessura di ponti chiodati di valenza storica n.3 pag.29

Fatigue properties and microstructural analysis of diecast AlSi11Cu2(Fe) alloy: effect of surface finishing n.11-12 pag.79 M. Merlin, D. Benasciutti, L. Lattanzi, A. Fortini, G. Timelli

LEGHE A MEMORIA DI FORMA / SHAPE MEMORY ALLOYS

S. Lorenzi, M. Cabrini, E. Rizzi, R. Ferrari, L. Coppola, G. Spirolazzi,

Transizione di fase indotta da deformazione in leghe a memoria

G. Pisanelli, C. Cioffi, E. Lizzori, T. Pastore

di forma NiTi n.7-8 pag.44

CORROSIONE NEL CALCESTRUZZO / CORROSION IN

C. Bellini, V. Di Cocco, F. Iacoviello, S. Natali

CONCRETE

LUCIDATURA ELETTROLITICA / ELECTROLYTIC

n.10 pag.24

Elettrolucidatura in soluzioni ecofriendly di campioni in

F. Bolzoni, M. Ormellese, E. Proverbio, MP. Pedeferri

Ti6Al4V ottenuti mediante Electron Beam Melting n.2 pag.74

Grandi tappe nello studio della corrosione delle armature

POLISHING

A. Acquesta, T. Monetta Risultati preliminari di caratterizzazione dei prodotti di corrosione in calcestruzzo armato soggetto a corrosione da cloruri per oltre 20 anni n.10 pag.35 N. Russo, F. Lollini, E. Rossi, T. G. Nijland, R. Polder

METALLI PREZIOSI / PRECIOUS METALS

Simulazione fisica dell’interazione plasma-metalli refrattari per applicazioni nucleari n.4 pag.06 E. Pakhomova, P. Gaudio, R. Montanari, M. Richetta, A. Varone

La Metallurgia Italiana - November/December 2021

pagina 107

Atti e notizie - AIM news

MATERIALI COMPOSITI / COMPOSITE MATERIALS

leghe di alluminio n.6 pag.09

compression n.5 pag.13

Brunelli, A. Martucci, M. Dabalà

Studio a compressione statica di pannelli honeycomb static G. Costanza, S. Ferrigno, M.E.Tata

L. Pezzato, A. G. Settimi, M. Calisi, A. Barduca, A. Longato, K.

Influenza delle condizioni di processo sulla morfologia dei rivestimenti di zinco n.6 pag.33

METALLURGIA DELLE POLVERI / POWDER METALLURGY

V. Di Cocco, F. Iacoviello, C. Bellini, S. Natali

una lega equiatomica ad alta entropia CoCrFeNiNb n.7-8 pag.08

Modellazione di processi di corrosione con il software COMSOL

Modello microstrutturale della resistenza a compressione di M. Cabibbo, F. Průša, S. Spigarelli, E. Santecchia, C. Paoletti

NICHEL E LEGHE DI NICHEL / NICKEL AND NICKEL

Multiphysics n.10 pag.63 E. V. Ghiggini, M. Baricco, C. Errigo, R. Ardino

ALLOYS

SALDATURA A FASCIO LASER / LASER BEAM WELDING

trattamento termico di leghe di Nichel fabbricate via Selective

nella saldatura al fascio laser n.4 pag.13

Effetto della pressatura isostatica a caldo (HIP) e del Laser Melting (SLM) n.2 pag.65 E. Bassini, A. Sivo, G. Marchese, P. Martelli, F. Calignano, S.

Modellazione analitica per la simulazione dei campi termici F. Giudice, S. Missori, A. Sili

Biamino, D. Ugues

SIMULAZIONE NUMERICA / NUMERICAL SIMULATION

NITRURAZIONE / NITRIDING

n.2 pag.81

Ottimizzazione

della

Numerical simulation of laser powder bed fusion processes microstruttura

e

delle

proprietà

micromeccaniche della coltre bianca sull’acciaio 42CrMo4 nitrurato e nitrocarburato n.9 pag.32

C. Ransenigo, M. B. Abrami, M. Tocci, A. Pola Sviluppo di modelli matematici per la progettazione di cicli

R. Sola, C. Martini, A. Morri, G. Mazzola, A. Zanotti, I. Zorzi

di ricottura di acciai alto-resistenziali mediante prove di

Modellazione di processi di corrosione con il software COMSOL

S. Canto, A. Ferraiuolo, S. Natali

Multiphysics n.10 pag.63

laboratorio e successiva validazione industriale n.4 pag.22

E. V. Ghiggini, M. Baricco, C. Errigo, R. Ardino

Riduzione dei difetti di bordo in laminati a caldo di

PRESSOCOLATA / DIE CASTING

deformazione plastica n.4 pag.31

Study of the effect of ultrasonic treatment in porosity and mechanical properties of cast parts n.11-12 pag.6

acciai inossidabili ferritici attraverso modellazione della S. Mancini, A. Di Schino, L. Langellotto

M. da Silva, S. Cruz, X. Planta, J. Tort, G. Aguirre

Sviluppo di un modello CFD del processo di gas-atomizzazione

Comparison between high-pressure die-cast and rheo-cast

morfologica delle polveri metalliche n.4 pag.47

aluminium-SiCp MMC; Wear and friction behaviour n.11-12 pag.13

per

la

previsione

della

distribuzione

dimensionale

a cura di: M. R. Ridolfi, P. Folgarait - Seamthesis Srl, Italia

E.W. Jarfors, C.K. Jammula, R. Ghasemi

Numerical simulation of the effects of a Phase n.11-12 pag.25

Micro spray technologies for an efficient die spraying in HPDC n.11-12 pag.85

SUPERLEGHE / SUPERALLOYS

M. Lutz

PROVE MECCANICHE / MECHANICAL TESTS

Comportamento a compressione a temperatura elevata di schiume di Al a porosità chiusa n.5 pag.44 G. Costanza, M. E. Tata

RIVESTIMENTI / COATINGS

Sviluppo di rivestimenti PEO contenenti fosfori YAG:Ce su

La Metallurgia Italiana - Novembre/Dicembre 2021

e

Z. Noohi, B. Niroumand, G. Timelli

Evoluzione microstrutturale e creep per la superlega NIMONIC 263: analisi e modellazione dei dati sperimentali n.7-8 pag.21 D. Della Torre, R. Donnini, M. Maldini, T. Ranucci, D. Ripamonti Microstructural restoration of long-term serviced cast Inconel 738 nickel superalloy turbine blade with difference solutioning and precipitation aging temperatures n.9 pag.40 N. Kiatwisarnkij, P. Fapinyo, K. Chanthawong, P. Horňak, P. Wangyao

pagina 108

Atti e notizie - AIM news

TECNOLOGIE ADDITIVE / ADDITIVE MANUFACTURING

Interazione laser-polveri metalliche ed effetti sul riciclo di materiale in processi di Laser Powder Bed Fusion (LPBF) n.2 pag.7 E. Santecchia, S. Spigarelli, C. Paoletti, M. Cabibbo Comportamento a creep di una lega AlSiMg prodotta da manifattura additiva n.2 pag.14 C. Paoletti, M. Cabibbo, E. Santecchia, S. Spigarelli Microstructural evolution induced by heat treatment in the Co28Cr6Mo alloy produced by Selective Laser Melting n.2 pag.22 L. Tonelli, I. Boromei, E. Liverani, L. Ceschini Binder jetting 3D printing of 316 stainless steel: influence of process parameters on microstructural and mechanical properties n.2 pag.31 N. Lecis, R. Beltrami, M. Mariani Ageing behavior of Beta-Ti21S produced by laser powder bed fusion n.2 pag.42 M. Pellizzari, A. Jam, V. Tonon, M. Benedetti, C. Lora

TITANIO E SUE LEGHE / TITANIUM AND ITS ALLOYS

Effetto della frequenza di anodizzazione e della polarizzazione catodica sulla resistenza a corrosione del titanio CP n.6 pag.23 L. Casanova, M.P. Pedeferri, M. V. Diamanti, M. Ormellese Sviluppo ed ottimizzazione di un rivestimento PEO su titanio per applicazioni ortopediche in differenti regimi di trattamento n.10 pag.46 M. Pavarini, M. Moscatelli, L. De Nardo, R. Chiesa Studio sulla delaminazione di ossidi PEO immersi in acido solforico mediante spettroscopia elettrochimica ad impedenza n.10 pag.52 L. Casanova, M. Gruarin, M.P. Pedeferri, M. Ormellese

TRIBOLOGIA / TRIBOLOGY

Lega A357 prodotta mediante SLM: studio del comportamento tribologico in condizioni di strisciamento non lubrificato n.5 pag.22 L. Lorenzetti, L. Tonelli, L. Ceschini, C. Martini

La Metallurgia Italiana - November/December 2021

pagina 109

Atti e notizie - AIM news

Indice autori / Author index Abrami, M. B. n.2 pag.81

Coppola, L. n.3 pag.29

Gruarin, M. n.10 pag.52

Acierno, S. n.7-8 pag.29

Corapi, D. n.2 pag.50

Gürcan, M. n.11-12 pag.37

Acquesta A. n.1 pag.06 - pag.31 - n.2

Costanza, G. n.5 pag.13 - pag.44

Gürsoy, Ö. n.11-12 pag.73

pag.74 - n.3 pag.38 - pag.44

Cruz, S. n.11-12 pag.6

Horňak, P. n.9 pag.40

Aguirre G. n.11-12 pag.6

D’Urso, G. n.3 pag.06

Iacoviello, F. n.6 pag.33 – n.7-8 pag.44

Angelini, E. n.10 pag.08

Da Silva, M. n.11-12 pag.6

Iannucci, L. n.10 pag.58

Angella, G. n.1, pag.22

Dabalà, M. n.5 pag.06 - n.6 pag.09 - pag.16

Ipock, A.W. n.3 pag.38 - pag.44

Ardino, R. n.10 pag.63

– n.7-8 pag.63

Jam, A. n.2 pag.42

Armakan E. n.11-12 pag.19

Dal Piaz, E. R. n.5 pag.06

Jammula, C.K. n.11-12 pag.13

Bacchi, L. n.9 pag.48

De Nardo, L. n.10 pag.46

Jarfors, E.W. n.11-12 pag.13

Barduca, A. n.6 pag.09

De Nisi, J. n.2 pag.50

Jayakumar, K. n.5 pag.32

Baricco, M. n.10 pag.63

Della Torre, D. n.7-8 pag.21

Kaciulis, S. n.9 pag.08

Bassini, E. n.2 pag.65

Di Cocco, V. n.6 pag.33 – n.7-8 pag.44

Kaya, A.Y. n.11-12 pag.19

Bellini, C. n.6 pag.33 – n.7-8 pag.44

Di Franco, F. n.3 pag.22

Khaskhoussi, A. n.3 pag.15 - n.10 pag.40

Beltrami, R. n.2 pag.31

Di Schino, A. n.2 pag.50 - n.4 pag.31

Kiatwisarnkij, N. n.9 pag.40

Benasciutti, D. n.11-12 pag.79

Diamanti, M. V. n.6 pag.23

Kobayashi, Y. n.11-12 pag.54

Benedetti, M. n.2 pag.42

Donato, N. n.10 pag.08

Krull, H.G. n.11-12 pag.37

Biamino, S. n.2 pag.65

Donnini, R. n.7-8 pag.21

Langellotto, L. n.4 pag.31

Bocchi, S. n.3 pag.06

Errigo, C. n.10 pag.63

Lara, A. n.11-12 pag.60

Bolli, E. n.9 pag.08

Fapinyo, P. n.9 pag.40

Lattanzi, L. n.11-12 pag.79

Bolzoni, F. n.10 pag.24

Fava, A. n.9 pag.08

Lazzaretto, A. n.9 pag.56

Bonollo, F. n.1, pag.22 - n.11-12 pag.49

Fernández Gutiérrez, R. n.11-12 pag.67

Lecis, N. n.2 pag.31

Boromei, I. n.2 pag.22

Ferraiuolo, A. n.4 pag.22

Leonelli, A. n.1 pag.06 - pag.31

Boscolo, D. n.11-12 pag.49

Ferrari, R. n.3 pag.29

Lepretti F. n.1 pag.37

Bravaccino F. n.1, pag.06 - pag.31 - n.3

Ferri, S. n.11-12 pag.31

Liverani, E. n.2 pag.22

pag.38 - pag.44

Ferrigno, S. n.5 pag.13

Lizzori, E. n.3 pag.29

Brunelli, K. n.6 pag.09 - pag.16

Folgarait, P. n.2 pag.50 - n.4 pag.47

Lollini, F. n.10 pag.18 - pag.30 - pag.35

Cabibbo M. n.2 pag.14 - pag.07 - n.7-8

Fortini, A. n.11-12 pag.79

Longato, A. n.6 pag.09

pag.08 - pag.29

Forzan, M. n.9 pag.15

Lora, C. n.2 pag.42

Cabrini, M. n.3 pag.06 - pag.29

Fracchia, E. n.1, pag.13 - n.11-12 pag.54

Lorenzetti, L. n.5 pag.22

Calabrese, L. n.3 pag.15 - n.10 pag.40

Franceschi, M. n.6 pag.16

Lorenzi, S. n.3 pag.06 - pag.29

Calignano, F. n.2 pag.65

Frómeta, D. n.11-12 pag.60

Lutz, M. n.11-12 pag.85

Calisi, M. n.6 pag.09

Galizzi, N. n.3 pag.06

Malburet, S. n.10 pag.58

Calliari, I. n.5 pag.06 - n.9 pag.15

Gariboldi E. n.11-12 pag.67

Maldini, M. n.7-8 pag.21

Canto, S. n.4 pag.22

Gastaldi, M. n.10 pag.18 pag.30

Mancini, S. n.4 pag.31

Carsana, M. n.10 pag.18

Gaudio, P. n.4 pag.06

Marchese, G. n.2 pag.65

Carugo, F. n.3 pag.06

Gennari, C. n.6 pag.16 - n.9 pag.15

Mariani, M. n.2 pag.31

Casanova, L. n.6 pag.23 - n.10 pag.52

Ghasemi, R. n.11-12 pag.13

Martelli, P. n.2 pag.65

Casellas, D. n.11-12 pag.60

Ghiara, G. n.10 pag.13

Martini, C. n.5 pag.22 - n.9 pag.32

Cason, C. n.7-8pag.63

Ghiggini, E. V. n.10 pag.63

Martucci, A. n.6 pag.09

Cerchier, P. n.5 pag.06

Giardini. C. n.3 pag.06

Matteis, P. n.7-8 pag.52

Ceschini, L. n.2 pag.22 - n.5 pag.22

Giudice, F. n.4 pag.13

Mazzola, G. n.9 pag.32

Chanthawong, K. n.9 pag.40

Gobber, F.S. n.11-12 pag.54

Merlin, M. n.11-12 pag.79

Chiesa, R. n.10 pag.46

Gobbo, R. n.9 pag.15

Meurisse, E. n.11-12 pag.43

Cioffi, C. n.3 pag.29

Graillot A. n.10 pag.58

Mezzi, A. n.9 pag.08

Colla, V. n.9 pag.48

Gramegna, N. n.11-12 pag.49

Missori, S. n.4 pag.13

Confalonieri, C. n.11-12 pag.67

Grassini, S. n.10 pag.08 - pag.58

Moedlinger, M. n.10 pag.13

La Metallurgia Italiana - Novembre/Dicembre 2021

pagina 110

Atti e notizie - AIM news

Monetta T. n.1 pag.06 - pag.31 - n. 2

Rossi, E. n.10 pag.35

Zambon, A. n.5 pag.06

pag.74 - n.3 pag.38 - pag.44

Rossi, P. n. 1 pag.31

Zanotti, A. n.9 pag.32

Montanari, R. n.4 pag.06 - n.9 pag.08

Rosso, M. n.1, pag.13 - n.11-12 pag.54

Zorzi I. n.9 pag.32

Montesano L., n.11-12 pag.31

Russo, N. n.10 pag.35

Morri, A. n.9 pag.32

Salanitro, A. n.10 pag.13

Moscatelli, M. n.10 pag.46

Sangermano, M. n.10 pag.58

Mus, C. n.11-12 pag.54

Santamaria, M. n.3 pag.22

Nardo, N. n.11-12 pag.49

Santecchia, E. n.2 pag.07 - pag.14 - n.7-8

Natali, S. n.4 pag.22 - n.6 pag.33 - n-7-8

pag.08

pag.44

Scarpa, G. n.11-12 pag.49

Niederhofer, P. n.11-12 pag.37

Scavino, G. n.7-8 pag.52

Nijland, T. G. n.10 pag.35

Schneiders, T. n.11-12 pag.37

Niroumand, B. n.11-12 pag.25

Schruf, I. n.11-12 pag.43

Noè, C. n.10 pag.58

Selvakumar, G. n.5 pag.32

Noohi, Z. n.11-12 pag.25

Settimi, A. G. n.6 pag.09

Ormellese, M. n.6 pag.23 - n.10 pag.24 -

Sili, A. n.4 pag.13

pag.52

Simonetto, E. n.9 pag.15

Özaydin, O. n.11-12 pag.19

Sinagra C. n.1 pag.06 - pag.31 - n.3 pag.38

Pakhomova, E. n.4 pag.06

- pag.44

Paoletti, C. n.2 pag.07- pag.14 - n.7-8

Sivo, A. n.2 pag.65

pag.08 - pag.29 - n.11-12 pag.60

Sola, R. n.9 pag.32

Parareda, S. n.11-12 pag.60

Spigarelli, S. n.2 pag.07 - pag.14 - n.7-8

Pastore, T. n.3 pag.06 - pag.29

pag.08

Pavarini, M. n.10 pag.46

Spirolazzi, G. n.3 pag.29

Pedeferri, M.P. n.6 pag.23 - n.10 pag.24 -

Stauder, B. n.11-12 pag.67

pag.52

Stolyarov, V. n.9 pag.15

Pellizzari, M. n.2 pag.42 - n.5 pag.06 -

Stornelli, G. n.2 pag.50

pag.09 - pag.16 - n.9 pag.15 - n-7-8 pag.63

Suresh, T. n.5 pag.32

Pigato, M. n.7-8 pag.63

Tarabotti, G. n.9 pag.15

Pisanelli, G. n.3 pag.29

Tarhouni, I. n.11-12 pag.60

Planta, X. n.11-12 pag.6

Tata, M. E. n.5. pag.13 - pag.44

Pola, A. n.11-12 pag.31

Testa, C. n.3 pag.06

Pola, A. n.2 pag.81

Timelli, G. n.1, pag.22 - n.11-12 pag.25 -

Polder, R. n.10 pag.35

pag.73 - pag.79

Poletti, M.C. n.11-12 pag.67

Tocci, M. n.2 pag.81 - n.11-12 pag.31

Proverbio, E. n.3 pag.15 - n.10 pag.24 -

Tonelli, L. n.2 pag.22 - n.5 pag.22

pag.40

Tonon, V. n.2 pag.42

Průša, F. n.7-8 pag.08

Tort, J. n.11-12 pag.6

Ramprakash, S. n.5 pag.32

Trasatti, S. n.10 pag.13

Ransenigo, C. n.2 pag.81

Ugues, D. n.2 pag.65

Ranucci, T. n.7-8 pag.21

Valentini, R. n.9 pag.48

Redaelli, E. n.10 pag.18

Van Soest, F. n.11-12 pag.37

Repitsch, C. n.2 pag.50

Varone, A. n.4 pag.06 - n.9 pag.08

Richetta, M. n.4 pag.06

Vietti, A. n.10 pag.08

Ridolfi, M.R. n.2 pag.50 - n.4 pag.47

Wang, R. n.11-12 pag.67

Ripamonti D. n.7-8 pag.21

Wangyao, P. n.9 pag.40

Rizzi, E. n.3 pag.29

Zaffora, A. n.3 pag.22

La Metallurgia Italiana - November/December 2021

pagina 111

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