AnIntroductiontoMetallic GlassesandAmorphous Metals
ZbigniewH.Stachurski
GangWang
XiaohuaTan
Elsevier
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Affineandnon-affinedeformation
StrainmeasuredbytheVoronoimethod(atomiclevel)...
StrainmeasuredbytheX-raymethod:crystallinesolids..
StrainmeasuredbytheX-raymethod:amorphoussolids.
Deformationinbulkmetallicglass
ElasticmodulusbytheX-raymethod..
DeformationinZr55 Al10 Ni5 Cu30 metallicglass...
DeformationinZr46.5 Cu45 Al7 Ti1.5 metallicglass..
DeformationinZr64 Cu16 Ni10 Al10 metallicglassundercooling
Deformationinthinfilmmetallicglass. .............................210
StructuralevolutioninZr50 Cu50 metallicglassduringcompression
StructuralevolutioninZr64.13 Cu15.75 Ni10.12 Al10 duringheating...........213
Changesinatomicstructurerevealedbyradialdistribution
Introduction
AristotlestatedatthebeginningofhisbookonMetaphysicsthat“allmen,bytheirnature,desireto know.”AristotlewasanancientGreekphilosopher(384–322BCE)andascientistborninthecity ofStagira,Chalkidiki,inthenorthofClassicalGreece.Allpeoplenaturallyarecuriousandacquire knowledgeforpracticalusageaswellasfordisseminatingknowledge.Anindicationofthisisour esteemforthesenses;forapartfromtheirusewevaluethemfortheirownsake,andmostofall,the senseofsight.Notonlywithaviewtoaction,butevenwhennoactioniscontemplated,weprefer sight,generallyspeaking,toalltheothersenses.Thereasonofthisisthatofallthesensessightbest helpsustoknowthings,andrevealsmanydistinctions.
Anotherphilosopher,XiangLiu,inWesternHanDynastyofancientChinasaid:“Seeingisbetter thanhearing,andpracticeisbetterthanseeing.”
Itisfrommemorythatpeopleacquireexperiencebecausenumerousmemoriesofthesamething eventuallyproducetheeffectofasingleexperience.Experienceseemsverysimilartoscienceandart, butactuallyitisthroughexperiencethatmenacquirescienceandart.
(a)TheGreatPyramidofGiza(ca.3000BCE);(b)abronzevaseofChina(ca.1300BCE);and(c)ironaxefrom Sweden(ca.1500ago).
Archaeologistsinvestigatehistoricandprehistoricsitesandphysicalartifactsfoundatthesitesto understandhumanactivitiesinthepast.Inthisprocesstheyrevealtheadvancementsofvariousaspects ofhumanlifeandreconstructhistoryofhumancivilizations.Asaresultoftheirextensivestudies,they havedefinedthelongspanofhumancivilizationintothreeerasdistinguishedbytheuseofmaterials aslistedbelow,andwithexamplesillustratedin Fig. 1.1:
AnIntroductiontoMetallicGlassesandAmorphousMetals. https://doi.org/10.1016/B978-0-12-819418-8.00005-X Copyright©2021HigherEducationPress.PublishedbyElsevierInc.Allrightsreserved.
FIGURE1.1
•TheStoneAge–prehistorytoca.3000BCE
•TheBronzeAge–approximately3000–1000BCE
•TheIronAge–approximately1000BCE–CE1000
Inmoderntimes,theperiodfrom1850to2000issometimesreferredtobydifferentnames:
•theAgeofSteel, •ortheAgeofPlastics, •ortheAgeofNanomaterials.
Perhapsmanydecadesfromnow,thisperiodoftimewillbereferredtoasTheAgeofNewMaterials, towhichmetallicglassesbelong.High-techcompanies,suchasSpaceX,OrbitalSciencesCorporation, orXCORAerospace,arerapidlydevelopingtransportationsystemsforexplorationoftheneighboring planets.Itismorethanlikelythatmetallicglasseswillplayasignificantroleintheseendeavors.Of course,itmayevenbecalledtheAgeofQuantumComputingorsomethingelse.
Anaccumulatedknowledge,whichcomprisesskills,art,techniques,andskillfulshapingandconstruction,constitutesanaccumulatedknow-howthatinvolves experience (skillsandfamiliarity)and requires holdinginmemory anamountofinformation(i.e.,anumberoffacts,orsimplyinformation). Notethat know-how issufficienttorepeattheactivityasmanytimesasrequired.Forexample,large man-madestonestructuresbegintoappeararound10,000yearsago.Suitablyshapedrockswereselectedforthepurpose,withtimbertrunksusedasrollers,andropesusedasslingsandforhoisting.In today’sterms,theconstructionofthestonestructurewouldbecalled civilengineering.However,from thisexperiencethemoreobservantindividualswouldholdinmemorynotonlytheeffortoflaborand theknow-howoftheconstruction,butalsosuchfactsashardnessandsurfacesmoothnessoftherock forlowerfriction,thestrengthofropeforpullingandliftingandthehardnessandresistancetosplitting oftreetrunksforrollingapplications.Allofthesearepropertiesofthematerialsusedintheengineering activitythatwouldberetainedinmemoryandinduecoursebecomeknowledgeofmaterials.
Thelongestexperiencewithmaterialswasthatwithstoneandwood,ofwhichstoneistheeverlastingasisevidentin Fig. 1.2.Smeltingandshapingofironfollowedtheexperienceandknow-how ofmakingbronzefromanearlierage,andwentonforcenturieswithoutsignificantadvances,until themiddleofthe19thcenturywhentheconfluenceoftwomajorfactorsrevolutionizedironsmelting intosteelmaking,supersedingtheageoldprocess.Thisnewmethodofsteelmaking,anditswide application,hadapronouncedeffectonourcivilizationinthemodernera.
Thefirstmajorcontributingfactorwastheexpansionofmanufacturingandconstruction,createdby demandsoftheindustrialrevolutioninthedevelopingworld,andhencetheneedforlargequantitiesof strongmaterialsformachinery,construction,andcivilengineeringconnectingcontinentsbyrailroads.
Thesecondessentialfactorwasthediscoverybychemists(metallurgists)that“pigiron”contained toomuchcarbondissolvedinit,whichhadtoberemovedbylengthyandcostlyreprocessingtogive amoreuseful“wrought”iron.Priortothattime,thecrudeironmaterialwasproducedintheblast furnace,usingrawmineralssuchasironore,lime,cokeforfuel,andotheringredients.Theproductof thisprocess,thepigiron,hadaveryhighcontentofcarbon,between4%and5%,togetherwithsilica andotherimpuritieswhichrendereditbrittleandnotofmuchusedirectly.(Thetraditionalmolds wereformedinsand,withacentralchannelbranchingintomanyindividualingotsatrightangles, resemblingalitterofsucklingpiglets,hencethenamepigiron).Chemistrywasdevelopingintoa powerfulscience,equippedwithanalyticaltoolsandtheoreticalunderstandingofthegas,liquid,and
Megalithicman-madestructuresfromtheStoneAge:(a)SinglechambertombinKorea(ca.the9thmillennium BCE);(b)StonestructuresinthemunicipalityofBorger-Odoorn,Netherlands(ca.the4thmillenniumBCE).
solidstate.Chemicalelementswerebeingdiscoveredandidentifiedatarapidrate.Alreadyin1722, RenéAntoineFerchaultdeRéaumurdemonstratedthatironwastransformedintosteelthroughthe absorptionofsomesubstance,laterfoundtobecarbon,forwhichA.L.Lavoisierproposedthename “carbon”in1789fromtheLatinwordfor“charcoal.”In1774,J.Priestleyfoundthatairisamixture ofgases,oneofwhichwasthehighlyreactivegashecalled“dephlogisticatedair,”lateridentifiedas oxygen,whichhadgreataffinityforcarbon.
In1856,theEnglishmanHenryBessemerbecameawareofthesignificanceoftheseeminglyunsaturateddemandforsteel,andsuddenlyrealizedthatcarboncouldbeburnedoutofthemolteniron byair.Hetookoutapatentonmakingsteeldirectlybyblowingairthroughthemoltenironmixture. Bytheturnofthecentury,largecompaniesweresetupintheUSAandEuropetomanufacturesteel bytheBessemermethod.Lateron,oxygensteelmakingeventuallyreplacedtheopenhearthfurnace. Oxygenwasliquefiedinastableformforthefirsttimein1883byPolishscientistsfromJagiellonian University,ZygmuntWróblewskiandKarolOlszewski.
Today,steel(togetherwithconcrete)isthemostwidelyusedmaterialintheworld.
Similarcircumstancesoccurredinthemiddleof20thcenturywithrespecttothediscoveryand developmentofmetallicglasses–thenewmaterials.Themostimportantapplicationofmetallicglasses isinthefieldofmagneticandferromagneticdevices.Theexceedinglylowmagnetizationlossofthese materialsisusedtoagoodadvantageinhighefficiencytransformersatlowfrequencypowerlines. Alsoelectronicsurveillancedevices(suchastheftcontrolpassiveIDtags)oftenusemetallicglasses becauseofthesespecialmagneticproperties.
Itisimportanttobringtonoticethefactthatamorphoussolids,otherthanmetallicglasses,are widelyused:silicaglassinwindows,inopticaldevices,andinopticalfibersfortelecommunication.
Glassy(amorphous)solidshavebeenpositivelyidentifiedintermsoftheiramorphousatomicstructureatthebeginningofthe20thcenturywiththeaidofX-raydiffractionstudies.Thefirststructure ofanamorphoussolid,namelythatofplainsilicaglass,wasidentifiedbyanX-rayscatteringstudy
FIGURE1.2
by(Warren, 1934)andmorerecentlycorroboratedbytheso-calledfluctuatingelectronmicroscopy. Chemistshadsomepriorideasaboutrandomnetworksandchainmoleculesasisknownfromthe worksofZachariasen(1932)andStaudinger(1933).Thetechnologyofprocessingofglassesandtheir manifoldusesareveryadvancedandextensive,yetthereisnoadequateunderlyingtheoryofamorphousstructureasforcrystallinesolids.Whatisgenerallyknownandacceptedatthisstageisthat amorphoussolidsdonotpossessasaruleanycrystallinity,andthattheatomicarrangementsareconsideredtoberandom,havingnolong-rangeorderasincrystals.Insomecircumstancestheyarecalled “frozenliquids.”
Theunderstandingoftheatomic-scalestructureofsolids(fromwhichmoderntechnologyand societybenefitsogreatly)hascomeabouttoalargedegreebecauseofthedevelopmentofthemethods ofgeometryandX-raycrystallography.FromthefirstdiscoveryofthediffractionofX-raysbyacrystal by(Friedrichetal., 1913)and(Bragg, 1913),tothepresentdaywhenstructuresoflargemoleculesare determinedroutinely,crystallographyhasdevelopedfromsmallbeginningstobecomeanenormously successfulandpowerfultoolforthestudyofatomicarrangementsinsolids.
TheothercontributingfactortowardsdiscoveringmetallicglasseswastheadvancementofMaterialsScience,especiallyinthefieldofplasticityofmetalsandmetallicalloys.Theoryofdislocations withintheorderedcrystallinestructure,andverificationoftheirexistencebyelectronmicroscopy,providedasoundbasisforaclearunderstandingoftheplasticityofmetals,especiallyofpuremetals,in termsofdislocations’motioninthepolycrystallinestructure.Soonafter,thestrengtheningmechanisms ofstrainhardening,precipitations,andalloyingwereidentified.Itwasconcludedthatmakingmetallic alloyswithsmallerandsmallergrainsizeleadstostep-wiseimprovementsinstrength.Eventually,in thelimitingcaseofzerograinsize,anamorphousstructurewasenvisioned,possessingmechanical strengthapproachingthatofthetheoreticalstrengthofmaterials.
Inthemid-20thcentury,thealloysystemofgold–silicon(Au–Si)waswellstudied,andwasknown tohaveahexagonalclose-packedcrystallinestructureinsolidifiedalloys.Interestingly,theAu–Si alloysystemshowsadeepeutecticatacompositionofapproximately20%atomicweightofSiin Au,withalowmeltingpointof636K,comparedtothemeltingpointofAuof1337K,and1687K forSi.Thiseutecticmelt,whenrapidlyquenchedonaspinningcopperwheel,solidifiedintothin ribbon-likeobjects,andappearedtohavenocrystallinityonthebasisofX-raydiffractionpatternof the“quenched”Au80 Si20 composition.Thiswasthefirstcaseofametallicamorphousalloyreportedin thescientificliterature.Veryhighcoolingrateshadtobeemployed,oftheorderof106 K/s,toproduce smallamountsoflongamorphousmetalofapproximately0.1 × 10mmincross-section,hencethe description“ribbon-like”metallicglasses.
Thefirstbulkmetallicglass(BMG),withcentimeterdimension,wastheternaryPd–Cu–Sialloy preparedbyChenetal.in1974.Asimplesuction-castingmethodwasusedtoformrodsofthemetallic glassatacoolingrateof103 K/s.In1982,TurnbullandcoworkerssuccessfullypreparedthePd–Ni–P BMGusingboronoxidefluxingmethodtopurifythemeltandtoeliminateheterogeneousnucleation. Theexperimentsshowedthataglasstransitiontemperature, Tg ≈ 2/3 Tm ,wasachievedwhenheterogeneousnucleationwassuppressed.Theingotwasofcentimetersize,solidifiedatcoolingratesofthe orderof10K/s.AlthoughtheformationofPd-basedBMGisanexcitingachievement,however,due tothehighcostofpalladiummetal,theexperimentswereonlyfollowedinacademiccircles,andthe interestfadedaftersomeyears.
Inthelate1980s,InoueandhiscoworkersinTohokuUniversityofJapansucceededinfinding newmulti-componentalloysystemsconsistingmainlyofcommonmetallicelementswithlowercrit-
Table1.1Propertiesofmetallicglasses(fromAshbyandGreer,2006).
Attributes
Attractiveproperties
general theabsenceofmicrostructuralfeaturessuchasgrainandphase boundariesallowscomponentswithfeaturesofnear-atomicscale mechanical highhardness,givinggoodwearandabrasionresistance highyieldstrength,veryhighfracturetoughness lowmechanicaldamping(lowdissipationlosses) thermal forsomemetallicglasses, Tg Tc ,allowingprocessingassuper-cooled liquid(thermo-plasticforming:injectionmolding,hotpressing,etc.)
Tg –glasstransitiontemperature, Tc –crystallizationtemperature electrical resistivityisalmostindependentoftemperature magnetic highmagneticpermeability chemical highcorrosionresistance processing lowsolidificationshrinkageandnograinstructuregive highprecisionandfinishincastings aesthetics veryhighsurfacepolishduetolackofmicrostructure durability highhardnessandcorrosionresistancegivesdurability
icalcoolingrates.Havingsystematicallyinvestigatedternaryalloysofrare-earthmaterialswithAl andferrousmetals,theyobservedexceptionalglassformingabilityintherare-earth-basedalloys,for example,La–Al–NiandLa–Al–Cu,bycastingthealloys’meltinwater-cooledCumolds.
Bytheearly2000s,manyhundredsofBMGshavebeenproducedaroundtheworld.Theinterest inamorphousmetallicmaterialsisevidencedbyaUSAcompany,LiquidMetal,whichintroducedthe firstcommercialamorphousalloy,Zr-basedVitreloy,in2003.TheVitreloyBMGhasbeenusedin sporting,medical,andindustrialproducts.
Metallicglassesseemunusual.Theyarehardandbrittlelikeglass,butnottransparent;theyhave thesofteningpointlikeglasswellbelowtheircrystallinemeltingpoint,yet,unlikeopticalglasses,they donotconductlight,butaregoodconductorsofelectricity.Indeed,metallicglassesarelikemetals andglasses,exhibitingsomepropertiescommontoboth.Theypossesthecharacteristicsofthetwo typesofmaterialsbecausethearrangementofatomsinmetallicglassesissimilartothoseinorganic andinorganicglasses,yetthechemistryandelectronicstructureisthatofmetals.Themainaimof thistextbookistodescribemetallicglassesintermsoftheirphysicalcharacteristics,theirusesand applications,themethodsoftheirmanufacture,andtheirinneratomicstructure.
Thechallengesofstudyinganddevelopingmetallicglassesarenumerous,carryingexcitementof newdiscoveriesandnewapplications,basedontheirinherentadvantagesshownin Tables 1.1 and 1.2.
Itcanbesaidwithahighdegreeofcertaintythatpetrolanddieselmotorcarshavelimitedlifeas theyarereachingtheirpeakinperformanceandefficiency,butcontinuetocontributesignificantlytothe environmentalpollution.Theywillgraduallydisappearfromourliveslikesteamenginesandsailing shipsofearliertimes.Electricmotorsarefarsuperiortoreciprocatingpistonengines,andtherefore,are thefutureofallourtransportationandmechanicalmovementactions.Theuseofelectricmotorsare presentlylimitedonlybythesupplyofhighcapacitybatteries.Metallicglassesareexcellentcandidates forelectricmotorapplications,andgreatadvancesintheiruseanddesignareanticipated.Imaginethe futurewithoutairpollutingcarsandtrucks.
Infact,theveryfirstmotorcarhadanelectricmotor(foracommercialexample,see Fig. 1.3)–it wasthelackofadequatebatteriesthatstalleditsprogress.FranceandtheGreatBritainwerethefirst
Table1.2Currentandpotentialapplicationsofmetallicglasses(Wangetal., 2004).
Property Primaryapplications Secondaryapplications
highstrength machinesanddevices
highhardness cuttingtools wearresistantmedicaldevices
highfracturetoughness diematerials
highreflectionratio opticalprecisionmaterials
highfrequencypermeability highmagnetostrictivematerials
highwearresistance medicaldevices
alloftheabove spaceapplications
FIGURE1.3
An1901advertisementforacommercialelectriccar.
nationstosupportthewidespreaddevelopmentofelectricvehiclesinthe1890s.FerdinandPorsche’s designandconstructionofanall-wheeldriveelectriccarinGermanywaspoweredbyanelectricmotor ineachhub,andhassetseveralspeedrecordsatthetime.Electricvehicleshaveanumberofsignificant advantagesovertheirpresentdaycompetitors.Mostimportantly,theydonothavethevibration,smell, andnoiseassociatedwithgasolineanddieselcars.Theyalsodonotrequiregearchanges.Iftheir batteriesarechargedfromrenewableenergysources,theireffectonairpollutionisclosetozeroby comparisonwithtoday’scars.
(Forcomparison,electricmotorsaretypically95%efficientintransforminginputenergyintorotationalenergy,whereasinternalcombustionenginesareonly35%efficientatbest–therestofthe fuel’scalorificvaluedissipatesasairfriction,andescapesasheatandexhaustgasses.Theefficiency ofsteamlocomotivesofthepastwasaslowas10%.)
Intelligentreflectionsontherelationshipbetweentheobservedpropertiesandperformanceofmaterialsleadtoenhancedpersonal knowledge,withsocialadvantagetopeoplecarryingoutengineering
activity.Thelevelofknowledgedependsontheabilitytoconceptualizetherelationshipsbetweenthe elementsoftheinformation,andanabilitytomanipulatetheconceptsandfactstoderivethelifeadvantage,whichleadsto understanding.(Knowledgemaybethoughtofasthedatabasecollectedby Facebook,whereasunderstandingisanalogoustothealgorithmwhichcharacterizeseachpersonon thedatabasebytheinformationheld.)Thus,scienceisabranchofknowledgedealingwithabodyof truthfulfactsarrangedtorevealgenerallaws,gainedthroughobservationandexperimentation.
MaterialsScience,abranchofthePhysicsofSolidState,isbasedontheknowledgeandunderstandingofthefollowingfundamentalrelationship:
atomic/molecularstructure → material’sproperties thatis,thechemistryandstructureofsolidsgovernsthebehaviorofthesolidmaterials.
TheuseofthisrelationshipforappliedpracticalendsisthefieldofMaterialsEngineering.An importantrelationshipexistsbetweenthemethodsandconditionsofprocessingofmaterialsandtheir finalmicrostructure.
processingofmaterials → material’smicrostructures
ThebasisofthefirstrelationshipcanbetracedbackinhistorytotheancientGreece,whenLeccipus ofMiletusandDemocritusofAbdera(inancientGreece)proposedthatmatteriscomposedofatoms (indivisiblevolume –derivedfromGreek).Furthermore,theyhypothesizedthatatomshaveshapesthat makethempossessandexhibitproperties,suchasacidity,sweetness,stickiness,andsmoothness,and allowthemtobondtomakeupothermatter.
Inthetworelationshipsabove,theterm“atomic/molecularstructure”referstothearrangementof atomsinthesolidmaterial,and“property”referstothephysical,chemical,electrical,mechanical, andotherpropertiesofmaterialsthatwemakeuseofinparticularapplications.Themetallicglasses connectthe“amorphous”structurewith“metallic”bonding;theyarethusexpectedtopossessunique propertiesthatdonotexistinothermaterials.
Indeed,itistheaimofthisbooktoprovidedeepinsightintotheserelationships,aswellasto consolidatetheexistingknowledgeonmetallicglassesandrelatedsubjects.Thehopeoftheauthorsis thatthistextbookprovidesmuchoftheinformationthestudentreaderissearchingfor,andfurthermore, thatitpointsthereadersaccuratelyandefficientlytoothersourceswheremoreinformationcanbe foundsothatdeeppersonalknowledgecanbeacquiredandenriched.
References
Bragg,W.L.,1913.Thediffractionofshortelectromagneticwavesbyacrystal.ProceedingsoftheCambridge PhilosophicalSociety17,43–57.
Friedrich,W.,Knipping,P.,Laue,M.,1913.X-raydiffractionfromsinglecrystals.AnnalsofPhysics346(10), 971–988.
Wang,W.H.,Dong,C.,Shek,C.H.,2004.Bulkmetallicglasses.MaterialsScience&Engineering.R,Reports44, 45–89.
Warren,B.E.,1934.X-raydeterminationofthestructureofglass.JournaloftheAmericanChemicalSociety17, 249–254.
Makingofmetallicglassesand applications
Applicationsofmetallicglasses
Aerospaceandbeyond
2.1
Metallicglasses(MGs)areconsideredasanovelclassofmaterials,differentfromcrystallinemetallic alloys.Overthepastdecades,experimentalandtheoreticalresearchershavedevotedtimeandeffortto understandandcharacterizethenatureofamorphoussolids.Metallicglassespossessexcellentproperties,andareregardedaspotentialmaterialsinmechanical,chemical,magnetic,andopticalengineering.
VariousmetallicglassyalloysbasedonZr-,Fe-,Ce-,Ti-,andMg-elementsattractgreatinterest forapplicationsinmedicine,electricalengineering,aeronautics,andastronautics.Therelevantresearch workhasbeenconductedinthefieldofspaceresearchanddevicesinaerospacevehicles,including protectiveshieldsandvariousaerospacecomponentssuchascompliantmechanisms,gears,magnetoelectriccomponents,solarwindcollectorplates,etc.
SpaceenvironmentissodifferentandcomplexcomparedthatontheEarth’ssurfacethatthe aerospacevehiclesaresubjectedtoextremeconditions:temperatureaslowas 200◦ C,extremehumidityanddesertenvironmentbeforelaunch,ultravioletexposure,ionirradiation,anddebrisstriking, whichdemandexceptionalpropertiesofthemetallicglassyalloysappliedinaerospace.Thestructural evolutionandperformanceofMGsatcryogenictemperatureshavebeenstudied,andaductile–brittle transitionwasobservedgoingfromlowertohighertemperatures,andvice-versa.TheionirradiationresistanceofMGshasalsobeeninvestigatedunderdifferentionsources.Therewasnosignificant damageobservedonTa38 Ni62 MGsurfaceirradiatedbyHe2+ ions.However,thermallyinducedpartial crystallizationoccurredunderprolongedexposureat360◦ CforCu60 Zr20 Hf10 Ti10 MG,whichmeans thatthisalloyisnotsuitableforirradiationenvironmentsforextendedperiodsoftime.Recently,a novelhigh-temperatureIr35 Ni20 Ta40 B5 MGalloyhasbeendevelopedbycombinatorialmethods,and itisexpectedthatitwillbeappliedinaerospaceunderbothhighandcryogenictemperatures.
Coldweldingoccursunderhighvacuum(i.e.,inaerospace)betweentheatomicallycleanmetal surfaces,evenwithoutheatapplied,andunderstaticcontact,causedbythemutualdiffusionofatoms
AnIntroductiontoMetallicGlassesandAmorphousMetals. https://doi.org/10.1016/B978-0-12-819418-8.00006-1 Copyright©2021HigherEducationPress.PublishedbyElsevierInc.Allrightsreserved.
10Chapter2 Makingofmetallicglassesandapplications atthecontactingsurfaces.Theservicelifeofthecomponentsduringstaticordynamicapplications wouldbeharmedbythestick–slipadhesivewear,andfrictionalwearduetothecoldweld.AnMoS2 compositemembranewaspreparedbychemicalplatingand/orelectroplatingmethodonthesurface ofanNi–Pamorphousalloyandanaluminiumalloymovingpart.Theadhesion(friction)coefficient betweenthecompositemembraneandtheMGwaslowerthan10 4 ,whilethatbetweenthetwoMG surfaceswasabout10 2 .AccordingtotheQ/WHJ21-93principle,theNi–P–MoS2 compositemembraneiswellsuitedforpreventingthecold-weldingeffect.
Protectiveshield
Withagrowingexplorationoftheouterspace,moreandmoremissionsarelaunchedbyNationalAeronauticsandSpaceAdministration(NASA),theEuropeanSpaceAgency(ESA),theJapanAerospace ExplorationAgency(JAXA),andtheChinaNationalSpaceAdministration(CNSA).Thespacevehicles,suchastheunmannedroboticspaceprobes,InternationalSpaceStation(ISS),spaceshuttles, andotherspacecraftwithhumansaboard,arethreatenedbythespacedebris,thenumberofwhichincreasesdaily.UntilJanuary2019,thenumberofdebriswasestimatedtobe34000forparticleslarger than10cminsize,900000for1to10cminsize,andmorethan128millionfor1mmto1cminsize, respectively.Thehugepopulationofspacedebrisinthesizerangefrom1mmto1cmisaseriousrisk tothespacecraft,fargreaterthanthatofmicrometeoroids.
Theso-called“Whippleprotectivestructure”developedbyFredWhipple(anAmericanastronomer)wasadoptedandisbeingassembledinspacecraftbymanyaerospaceagencies,inwhich thematerialoftheoutershieldisofparamountimportancetoprotectthemaincraftduringmicrometeoroidsandorbitaldebris(MMOD)impacts.Incontrasttomonolithicshieldingoftheearlyspacecraft, Whippleshieldsconsistofarelativelythinouterbumperspacedsomedistancefromthemainspacecraftwall.Thebumperisnotexpectedtostoptheincomingparticleorevenremovemuchofitsenergy, butrathertobreakitupanddisperseit,dividingtheoriginalparticleenergyamongmanyfragments thatfanoutbetweenthebumperandtheouterspacecraftwall.
Theidealmaterialforprotectiveshieldisrequiredtohavehighhardnessinordertobeabletobreak uptheparticles,andlowdensitytominimizetheweight.Anotherdesiredpropertyisalowmelting point,sothatthedebriswouldevaporateittopreventgenerationofcollisiondebrisduringanMMOD impact.Analuminiumalloyisthematerialusedcurrentlyinthespacecraftprotectiveshieldbecauseof therelativelylowpriceandadequateperformance.AresearchgroupfromNASAreportedimpressive testresultsformetallicglassesduringhyper-velocityimpact(HVI)tests.
Inthefirsttrial,Zr36 6 Ti31 4 Nb7 Cu5 9 Be19 1 MGcompositewasadoptedforconstructingthecellularstructuresandsubjectedtoimpactwithvelocitiesrangingfrom0.8to3.0km/s,usingaluminium sphereswithadiameterof3.17mmastheimpactingparticles.Singlelayersmadefromthesame materialwereimpactedbythealuminiumprojectiles,andtheresultswerecontrastedwiththoseof amulti-facetedegg-boxstructure.Theresultsshowedthatthethicknessrequiredforthefacesheets wasgreaterthanthatintheegg-boxstructuretopreventpenetration.ThecorrugatedpanelscoulddiffusethedebrisproducedbythebumperduringanMMODimpactmoresignificantlycomparedtothe single-wallshield.Inthistrial,MGswererepeatedlycastatlowcostintoacomplexhoneycomb(eggbox)structure.TheconstructionofasinglehoneycombstructurebyweldingisdifficultusingMGs. AmethodforjoiningMGcompositescanusecapacitivedischarge.Duringtheprocess,MGsshowa near-constantelectricalresistivityasafunctionoftemperatureresultingfromtherandomatomicarrangements.Thematrixofthepanelcanbeheatedtoapproximately700◦ Cin10millisecondswhen
compositepanelsareplacedbetweentwocopperelectrodeplatesanddischargedbyacapacitor.The nodesofeachpanelwouldfuseandconnectintoasinglepiecebyapplyingaforgingloadduring discharge.Thetechniqueallowsthefabricationofacellularstructuredescribedinthepatent,whichis well-suitedforspacecraftshieldsormilitaryvehicledoorpanelswithhighest-strengthandmostenergy absorption.
InthesecondtestseriesforZr41 2 Ti13 8 Cu12 5 Ni10 Be22 5 andZr36 6 Ti31 4 Nb7 Cu5 9 Be19 1 MGs, compositesweredesignedtoestimatetheballisticlimitforbulkMGsandtheircompositesandto investigatespallingbehavioratvelocitiesfrom0.8to2.8km/s.TheresultsshowedexcellentcombinationsofhardnessandtoughnessofMGsforuseasshields.Comparedtoasingleshieldstructure, multi-layershieldsaremoreeffectiveindiffusingtheimpactenergy.
Forthethirdseries,theWhippleshieldsincorporatedlayersofFe65 Si15 B20 MGandwereassessed atvelocitiesof6.97–7.05km/sthroughHVItests.ThiscompositionMGhasalowglass-formingability andcanbeproducedinaribbonwhichisonly23µmthick.Ashieldcomprising21cmsquaresheets stackedtogetherfromindividualribbonlayersallowedtheWhipplestructuretomaintainthesameareal densityastheactualISSmodulebaseline.Intheresults,theprojectilepenetratedthebaselinesample butdidnotpenetratetheshieldwithintermediatelayersofMGsundertheidenticalconditionswitha baselineWhippleshieldcurrentlyusedontheISS.ItisclaimedthatthisMGcanbeareplacementfor thefabriclayersintheWhippleshieldarchitecture.
AnothergroupconductedtheHVItestsusingFe77 Si14 B9 MGfilmcoatedontheLY12Alaluminiumalloytobeusedasthefrontbumperofatwo-layerWhippleshieldwithvelocitiesranging from3.44to5.70km/s.TheMGfilmwasfabricatedbythethermalspraycoatingtechniquetodeposit athicknessof0.15mm.CombiningtherigidsubstrateprovidedbyaluminiumandthehardFeMG film,thereinforcedbumpershowedbetterperformancethanthetraditionalone,whichmaybedueto thehigherdensity,lowerspecificheat,andnotsohighmeltingtemperatureoftheFe-basedamorphous alloy.However,thedensityenhancedbyMGfilmontheAlsubstrateislimited.Anotheradvantage ofMGinthiscaseisthathighershockpressurescanbegeneratedinthereinforcedbumpertoinduce ahighertemperatureriseintheprojectile,whichwillpromoteprojectilefragmentationandprovide betterprotectionperformancecomparedtothetraditionalone.
Inanotherdevelopment,bulkZr51 Ti5 Ni10 Cu25 Al9 MGwasfabricatedbycoppermoldcastingwith asizeof3.5mm × 45mm × 45mm.TheHVIexperimentswereconductedusingatwo-stagegas gunwithseveralvelocitiesoftheprojectiles,rangingfrom1.40to4.27km/s.Afterthehyper-velocity tests,damagemorphologyofthefrontbumpwasanalyzed.
Applicationascompliantmechanisms
Variousmechanismsareusedinaerospaceequipmentasrequiredbecauseoftheirexcellentability toapplyforce,translationandrotationmovement,inkinematicpairs,gears,linkages,andflexurecompliantmechanisms.Thesemechanismshavestrictrequirementsofdimensionalaccuracy,high strength,andelasticity,aswellaslowwearandlowcoefficientofthermalexpansion.Especially single-piecemechanismsarepreferredtoreducetheassemblingtoleranceandenhancestability.MGs combinetheadvantagesofhighstrength,highelasticity,andgoodprocessability.Twotypicalmetallic glasses,i.e.,Zr41 2 Ti13 8 Ni10 Cu12 5 Be22 5 andZr44 Ti11 Ni10 Cu10 Be25 ,areusedtofabricatebistable compliantmechanisms.Sometraditionalmaterials,suchasthebestperformanceTi-6Al-4Valloy amongthecrystallinematerials,arealsoadoptedtobecontrastedinexperiments.Itisdemonstrated
12Chapter2
Makingofmetallicglassesandapplications thatdevicesmadefromMGscanprovidealargersafetyfactorforsimilarly-sizedcompliantmechanisms,ortheycanbefabricatedtohavemuchsmallersizesbecauseofhigherstrengthcomparedto theTi-6Al-4Valloy.Duringthefabricationprocess,MGscanbemeltedandinjectedintoacomplex moldatalowtemperaturewithoutpost-processing(polishing)procedurewhichalsolowerstheproductioncosts.Forthedesignchallenge,MGsexhibitbettermanufacturabilitywithoutpost-machining toovercometheproblemofthermalexpansionmismatchandpreciseassembly.Somepatentshave beenappliedinthisfieldrecently.
Ball-and-conelocatorsarestandardlatchingmechanismswithadeployablestructureforaerospace vehicles,inwhichthepreferredmaterialshouldhavelowdensityandhighperformance,highhardness andductility,lowmeltingpoint,tolerancetocryogeniccircumstanceandcryogenic-thermalcycling, andbecompatiblewithflight-gradeepoxymaterial.TheperformanceofTi-basedMGsandtheircompositeswasstudiedthroughpush-outtests,four-pointbending,andcryogenic–thermalcyclingtests. ItwasshownthatthelocatorinsetsusingTi44 Zr20 Cu5 V5 Al7 Be19 MGwouldbe39.5%lighterwhen comparedto440stainlesssteel,indicatingthegreatestpotentialtoreplacethistraditionalsteelmaterial.AcompositionofTi40 Zr20 Cu10 Be30 isyetanotheralternativetoconsiderbecauseofitshigh glass-formingabilityandattractivemechanicalproperties.
Applicationasgears
Unlikethetraditionalsteelmaterials,metallicglassesbecomemoreductile(lessbrittle)inextreme cold,whichmakesthemmoreappropriateforrobotsworkinginspaceoronicyplanets.TheresearchersandengineersfromNASAJetPropulsionLaboratory(JPL)designedatesttoestimatethe potentialbenefitofmetallicglassincreatingroboticgearsforspacecomparedtoceramicsandsteels. Agearisessentialintheprecisionroboticsandrequiredwhentherobotsperforminspacemissions. ResultsfromJPLshowthatthegearsmadefrommetallicglasscantransmithightorqueandsmooth turningwithoutlubricantevenattemperaturesaslowas76K.Amongvariousmetallicglasses,CuZrbasedCu43 Zr43 Al7 Be7 MGexhibitsexcellentwear-resistancewitha60%improvementthrougha superiormethodofgear-to-geartestingcomparedtohigh-performancesteelVascomaxC300whichis usedcurrentlybyNASAonMarsroverCuriosity.Itisindicatedthatthenatureoftoughnessismore importantthanhardnesswhenconsideringgearwear,whichiscontrarytotraditionalclaims.Inthis test,theMGsgearwasfabricatedbyanet-shapedcastingwithoutpost-machining,whichcanimprove thewear-performanceandlifetimeofMGgearbutwithasuperiorsurfacequalitytothatofelectric dischargemachinedgears.Somepatentshavebeenappliedforinthisfieldrecently.Examplesofgears manufacturedfrommetallicglassesareshownin Fig. 2.1.1.
Applicationasmirrors
Metallicglassesweremanufacturedintomirrorsforpossessingtheabilityofcastingintoboththe mirrorsurfaceandbacking,allinonestep.Duetotheexcellentscratchresistanceandpotentiallylow costoffabrication,metallicglassesareinvaluableinspaceapplications.
AnotherapplicationformetallicmirrorsisinITER(“TheWay”inLatin)asoneofthemostambitiousenergyprojectsintheworldtoday.InSouthernFrance,35nationsarecollaboratingtobuildthe world’slargesttokamak,amagneticfusiondevicethathasbeendesignedtoprovethefeasibilityof fusion.AsimilarprojectisunderwayintheUSA.TheobjectiveoftheITERprogramistounderstand andcontrolnuclearfusion.
FIGURE2.1.1
Gearsmanufacturedformetallicglasses.
TwoITERrequirementsonshuttersareunprecedentedoncontemporarymachines.First,plasmanearcomponentsmustwithstandsignificantneutronfluxesoftheorderof1014 s 1 cm 2 withenergies upto14MeV,leadingtovolumetricheatingandmaterialdegradation.Second,accessibilityformaintenanceandreplacementisverylimitedformultiplereasons,requiringthelifetimeofshuttersbe ≥ 20 years.
MetalmirrorsareforeseenforopticaldiagnosticsystemsofITER.However,thesemirrors,subjectedtointenseirradiationbyX-rays,gammarays,neutrons,andchargedparticlesofwideenergy ranges,quicklyloosetheoriginalopticalpropertiesduetosputtering,erosion,deposition,accumulationofgasses,creationofdefects,ionimplantation,etc.Therefore,theselectionofthemirrormaterials reliesprimarilyontheresistancetodegradationthroughplasmaexposures.Amongthemaincandidate mirrormaterialsarehigh-Zmetalslikemolybdenum,tungsten,andrhodium.Laboratoryandtokamakexperimentsshowedthatpolycrystallinemetallicmirrorscouldnotsustaintheirreflectivities undererosion-dominatedconditionsduetotheincreaseinsurfaceroughness.Single-crystalmaterials suchasmolybdenumandtungstenlargelyovercometheheterogeneouserosionproblemofdifferentlyorientatedgrainsandcanpreservetheiropticalpropertiesundererosionconditionsforlongerperiods oftimeasconfirmedbylaboratorytests.
Amorphousalloys,ormetallicglasses,arehomogeneousstructureswithoutgrainboundariesthat maywellresistheterogeneoussputteringanderosions.Bulkamorphousalloyshavelargeglassformingabilitiesandhighstrengthsinsharpcontrasttotraditionalamorphousalloys.Forinstance, bulkamorphousalloyZr41 2 Ti13 8 Cu12 5 Ni10 Be22 5 wasshowntohaverelativeslowdecreaseinspecularreflectivity. Fig. 2.1.2 showsaspacemirrormadefromtheabovemetallicglassalloy.
FIGURE2.1.2
SpacemirrormadefromZr-basedmetallicglass(VitreloyI).
Applicationtocorrosionresistance
Tooptimizetheperformanceandcostswhileminimizingtheweightofthecomponentsinaerospace vehicles,afiber–metallaminateisusedincommercialaircraft,madeupofalternatinglayersoffiberreinforcedpolymer,i.e.,glassfiber-reinforcedepoxyandaluminiummetallicalloy.Thecombination betweencarbonfibercompositeandaluminiumisnotfeasiblebecauseofgalvaniccorrosioninducedat thecontactofthetwomaterialswhensubjectedtodifferentelectricalpotential.Theisotropicstructure andabsenceofcrystalboundariesinmetallicglassesassistcorrosionresistance.IthasbeendemonstratedthatametallicglassreplacingAlexhibitssuperiorcorrosionresistance(approximately20times better)aswellasgoodmechanicalperformance,especiallytheretentionofelasticbehaviortohigher strains,duetotheincorporationofalternativecomponentmaterials.
Applicationtosolarwindcollection
Metallicglasseswerefabricatedintotargetstobeexposedtosolarcorpuscularradiationwiththeaim toexploretheactivityofsolarwind,asconductedbyNASAontheGenesisDiscoveryMission.Itis consideredthatmetallicglassespossessvariousexpectedadvantagesthatmeetthedemandsforsolar windcollection.Duetotheisotropicstructureandabsenceofcrystallattice,fractionationandlossof solarwindalongthepreferreddiffusionpathsoncrystalplanesiseliminated.Furthermore,homogeneousetchingallowsthehighresolutiondepthprofilingoftheisotopiccompositionandtheamount ofimplantedsolarnoblegases.Thisdatademonstratesthecompositionalinformationaboutthesolar windandpotentialvariationsasafunctionofenergyoftheradiation.However,itwasalsonotedthat metallicglassisnotperfectlysuitablefortheprecisedeterminationoftheisotopicandelementalcompositionofbulksolarwindnoblegasesasaconsequenceofcorrectionsforlightelementscompared toahighproportionofheavyelementsintheglass. Fig. 2.1.3 showsasolarwindcollectiondevice,of theNASAspacemission,comprisinghexagonalcollectorsmadefromsiliconandotherpurematerials, includingmetallicglass.Otherexamplesofusingmetallicglassesforspaceapplicationsareshownin Fig. 2.1.4.
FIGURE2.1.3
In2004,NASA’s“Genesis”solarwindcollectiondevice.
Applicationasmagneticsensors
Magneticsensorsworkindeepaerospaceexplorationtodetecttheambientmagneticfieldvectoraccuratelyandtodiscriminatethesourcesofstraymagneticfieldsproducedbymechanical,electrical, andelectronicsystemsonaerospacevehicles.Amorphousgiantmagnetoimpedance(GMI)sensors areusedinassembledspacemagneticinstruments.Ontheotherhand,amorphousGMIsensorsare ideallyusedforthecontrolofthegearspeedandprecisedeterminationofthegear-toothpositionin aircraftenginesduetotheultrahighsensitivityandsmallsize.Co-/Fe-basedamorphousribbonsare theidealmaterialsduetotheexcellentsoftmagneticproperties,i.e.,highsaturatedmagnetization, lowcoercivity,highmagneticpermeability,andgoodmechanicalproperties.Whenaerospacevehiclesareworking,somefunctionalcomponents(i.e.,traveling-wavetube,rubidiumclock)areaffected easilybyamagneticfield.Thusmagneticshieldingisnecessarytoprotectthosecomponents.The amorphous/nano-crystallinesoftmagneticmaterialsareapromisingcandidateforuseasshielding materials,inwhichFeNi-/Co-basedamorphousalloysshowbettershieldingeffectiveness.
NASA’sGenesisspacecraftisthefirstmissiontocollectandreturnsamplesofthesolarwind— fastmovingparticlesfromtheSun.Adiskmadeofauniqueformulationofbulkmetallicglasswas createdspeciallyforGenesisinacollaborativeeffortwiththeHowmetCorporation.Thesurfacesof metallicglasseswillbedissolvedevenly,allowingthecapturedionstobereleasedinequallayersby sophisticatedacidetchingtechniques.
Inthe1990s,ametallicglass(Metglass®)wasdevelopedintoalightweightsearch-coilantenna orsensorincludingamulti-turnelectromagneticinductioncoilwoundonaspooltypecoilform.The limitationsoflightweight,size,andlocationareconstrainedbysurvivalinhighstresstypicallyused inspace.Thoughthedensityofametallicglassisabouttwicethatofferrite,only7%asmuchof themetallicglassmaterialisneededforaconfigurationofequaleffectiveness.Theamorphousribbon VITROVAC6025(typicalcomposition,Co66 Fe4 Mo2 Si16 B12 )wasusedinthevectormagnetometer sensoronboardtheAstrid-2satellitemadeasacompactring-coretomapthemagneticfield.Themissions“NewMillenniumProgramme”werelaunchedbyNASAtoestablishtheEarth’smagnetosphere, whereanetworkofnano-satellitesensorsweredesignedin2003forthispurpose.
Spaceapplicationsofmetallicglasses.
TheCo67 Fe3 Cr3 B12 Si15 amorphousalloywasusedtoinvestigatethemodelingofhysteresisloops ofultrahighpermeabilityalloysforspaceapplication.Aring-shapedcorewithasmallcross-section, with400sensingwindings,wasstudiedtoensurehighmeasurementsignal,whichindicatestheJiles–Athertonmodelissuitableformodelingtheultrasoftamorphousalloy.Itwasannouncedthatthisresult isappliedin“SmallExplorerforAdvancedMissions”and“DigitalMagnetometerforMicrosatellites Lemi-020”projectswhichaimtolowerthenoisethroughthedesignanddevelopmentofmagnetic fluxgatesensors.
Applicationassuper-conductingsensor
AprogramwasdevisedbyNASAtomeasureabroadelectromagneticspectrumatsub-millimeterand far-infraredwavelengths.Thus,anactivelycooledanddirectradiationdetectorwithhighsensitivity wasrequired,whichcanaccomplishthetaskssuchasX-raydetectionformedicalimaging,chemicalanalysisforMaterialsScienceatX-raywavelengths,andradiationdetectorsfornuclearforensics. Comparedtothetraditionalstate-of-the-artdetector,super-conductingmetallicglasstransition-edge sensorsCu35 Ti65 andCu60 Zr40 exhibitvariousadvantages,includingimprovedenergyresolution, lowerexcessnoise.Anamorphousalloymayalsobeaself-absorberofradiation(with4dand5dtransitionmetaladditionstoalloy(s)).Itcanpreciselycontrolsuper-conductingtransitiontemperature, Tc , havesimplifieddetectorarchitecture,aswellasmechanicallyandchemicallyrobustdesign.
Ti-basedmetallicglasses,whenmadeintothinpipes,havehightensilestrengthof2100MPa, elasticelongationof2%,andhighcorrosionresistance.Usingtheseproperties,aTi–Zr–Cu–Ni–Sn metallicglasswasusedtoimprovethesensitivityofaCoriolisflowmeter.Thisflowmeterisabout 28–53timesmoresensitivethanconventionalmeters,whichcanbeappliedinfossil-fuel,chemical, environmental,semiconductor,andmedicalscienceindustry.
FIGURE2.1.4
