WEDNESDAY AM
11:05 AM Polycrystal-Plasticity Simulation of Roping in AA6xxx Automotive Sheet Alloys: Olaf Engler1; Carmen Schäfer1; Henk-Jan Brinkman1; 1 Hydro Aluminium Rolled Products GmbH The occurrence of roping in AA6xxx sheet alloys for car body applications is caused by the collective deformation of band-like clusters of grains with similar crystallographic orientation. In this paper large-scale orientation maps obtained by electron back-scattered diffraction (EBSD) are input into a visco-plastic self-consistent polycrystal- plasticity model to analyze the strain anisotropy caused by the topographic arrangement of the recrystallization texture orientations. (i) the local dispersion in strain rate components is analyzed for the EBSD maps obtained in the sheet plane to confirm the effect of orientation clustering on roping; (ii) narrow bands in the EBSD maps acquired from the rolling direction are considered to study the impact of through-thickness texture topography on the macroscopic strain response from band to band. The polycrystalplasticity roping model is applied to two sheets distinguished by different levels of roping. 11:25 AM Properties of Free-Machining Aluminum Alloys at Elevated Temperatures: Jiri Faltus1; Miroslav Karlik2; Petr Hausild2; 1Research Institute for Metals; 2Czech Technical University in Prague In areas close to the cutting tool the workpieces being dry machined could be heated up to 350°C and they may be impact loaded. Therefore it is of interest to study mechanical properties of corresponding materials at elevated temperatures. Free-machining alloys of Al-Cu and Al-MgSi systems containing Pb, Bi and Sn additions (AA2011, AA2111B, AA6262, and AA6023) were subjected to Charpy U notch impact test at the temperatures ranging from 20 to 350°C. The tested alloys show a sharp drop in notch impact strength KU at different temperatures. This drop of KU is caused by liquid metal embrittlement due to the melting of low-melting point dispersed phases which is documented by differential scanning calorimetry. Fracture surfaces of the specimens were observed using a scanning electron microscope. At room temperature, the fractures of all studied alloys exhibited similar ductile dimple fracture micromorphology, at elevated temperatures, numerous secondary intergranular cracks were observed.
ICME Keynote
Program Organizers: William Cassada, Alcoa Technical Center; Hasso Weiland, Alcoa Technical Center; Anthony Rollett, Carnegie Mellon University Symposium Organizers: John Allison, University of Michigan; George Spanos, The Minerals, Metals & Materials Society Wednesday AM June 6, 2012
Room: Rangos I Location: University Student Center
Technical Program
Session Chair: John Allison, The University of Michigan
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8:15 AM Keynote Develop ICME Tool for High Ductility Cast Aluminum Alloys for Automotive Body Applications: Mei Li1; J. Zindel1; L. Godlewski1; Xuming Su1; 1Ford Motor Company One heat treatable high ductility Al-Si-Mg alloy was investigated in this study. To achieve the full potential of strength and ductility of this alloy, super vacuum die casting (SVDC) process was used to produce the high integrity Al cast components free of air entrapment. A semi-empirical model based on Shercliff and Ashby’s process model for age hardened Al alloys and experimental data were developed. The model can predict the effect of solidification time, aging temperature and time on yield strength. A quality mapping approach was adopted to predict the local ductility based on the predicted criteria functions from commercial casting simulation
program MAGMAsoftTM and experimental data. A new materials card was then built for crash performance analysis in LS-DYNA which includes the impact of local yield strength and ductility. Finally this ICME tool was validated on component level three-point and four-point bending testings.
ICME 1
Program Organizers: William Cassada, Alcoa Technical Center; Hasso Weiland, Alcoa Technical Center; Anthony Rollett, Carnegie Mellon University Symposium Organizers: John Allison, University of Michigan; George Spanos, The Minerals, Metals & Materials Society Wednesday AM June 6, 2012
Room: Dowd Location: University Student Center
Session Chair: George Spanos, TMS 9:15 AM Utilisation of Atom Probe Data to Model Precipitation and Strengthening in an Al-Mg-Si-Cu Alloy During Natural Ageing and Early-Stage Artificial Ageing: Dacian Tomus1; Paul Rometsch1; Malcolm Couper1; Chris Davies1; Lingfei Cao1; 1Monash University An Al-Mg-Si-Cu alloy was artificially aged for 0.13, 0.5 or 2 hours at 170°C after natural ageing times of 0.03, 3 or 168 hours. Three dimensional atom probe (3DAP) analysis and tensile testing were performed in the artificially aged and naturally aged conditions. The experimental data were used to determine model inputs such as particle size distributions and volume fractions of particles. The principle of the model is to numerically simulate the isothermal transformation of clusters, zones and/or precipitates by dividing the starting particle distribution into a series of discrete size classes and control volumes. Standard physically-based equations are used to simulate particle growth and/or dissolution by adjusting enthalpy, entropy and interfacial energy values to obtain a good fit between model predictions and 3DAP results. The predicted particle size distributions and volume fractions are then used to model yield strengths in a wide range of naturally aged and under-aged conditions. 9:35 AM Ab Initio Simulations of Vacancy-Solute Clusters in Al-Mg-Si and Al-Zn-Mg Alloys: Peter Lang1; Peter Mohn2; Ahmad Falahati2; Ernst Kozeschnik2; 1Materials Center Leoben Forschungs GmbH; 2Vienna University of Technology The coherent fcc (face-centred-cubic) based cluster stability of Al-Mg-Si and Al-Zn-Mg alloys is studied theoretically using augmented plane wave density functional theory calculations of a periodically repeated supercell containing 32 atoms. In particular, the presence of vacancies within the structure of Mga-Sib±Vac and Znd-Mge±Vaf clusters is investigated in detail. These fcc type arrays of solutes are considered to bind with vacancies. The binding energies between two substitutional elements, Mg and Si as well as Zn and Mg, and same arrangements bound to one vacancy in a fcc aluminium matrix are calculated. The binding energies of the coclusters are taken as reference energies to compare the binding energies of two atom co-clusters to a vacancy in different constellations. These energies are used to predict formations of very early clusters containing single vacancies. Energetically more favourable structures are obtained and discussed. 9:55 AM Break 10:25 AM Modeling Precipitation in Al-Mg-Si Alloy – the Effect of Deformation: Ahmad Falahati1; Mathieu Bolez2; Mohammad Ahmadi1; Jun Wu1; Ernst Kozeschnik1; 1Vienna University of Technology; 2Ecole Polytechnique de l’université de Nantes The diffusion kinetics in crystals is governed by the density of vacant