Modeling Static Recrystallization in Al-Mg Alloys
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Modeling Static Recrystallization in Al-Mg Alloys HEINRICH BUKEN and ERNST KOZESCHNIK In the present work, the influence of Mg on recrystallization kinetics in Al is analyzed by computer simulation. A comprehensive state parameter-based microstructure model is developed, which describes recrystallization in terms of nucleation and growth. The mechanism of solute drag is fully incorporated, thus accounting for the decrease of grain boundary mobility in the presence of impurity atoms. On the basis of the present approach, the solute binding energy between Mg atoms and grain boundaries is assessed and compared to experimentally measured values. Furthermore, the influence of Mg on dislocation production during strain hardening is modeled. The simulations of the composition and temperature-dependent recrystallization kinetics are verified on experimental studies where excellent agreement is achieved. Both simulation and experiment show that increasing Mg content first decelerates and, later on, accelerates recrystallization kinetics. https://doi.org/10.1007/s11661-020-06100-9 Ó The Author(s) 2020
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INTRODUCTION
THE control of microstructure evolution during processing of Mg-alloyed Al materials is a key factor for determining the final mechanical–technological properties of the material. Mg is a widely used element in Al alloys, especially in the 5xxx and 6xxx series. On the one hand, Mg segregates into grain boundaries and reduces the mobility of the moving boundary by several orders of magnitude in comparison to pure Al.[1] This so-called solute drag effect[2] is caused by solute atoms being dragged along with the moving grain boundary, thus exerting a restraining force against the movement of the grain boundary. As a result, microstructural processes involving the motion of high-angle grain boundaries (HAGB) and low-angle grain boundaries (LAGB) can be severely slowed down by the presence of impurity atoms.[1,3] On the other hand, an increased Mg content promotes a higher strain-hardening rate, which, at identical strain, induces a higher dislocation density.[4,5] As a result, the driving pressure for recrystallization increases, thus accelerating the observed recrystallization kinetics. Koizumi et al.[6] have performed recrystallization experiments in Al-Mg alloys, observing that an increase of the Mg content first leads HEINRICH BUKEN is with the Primetals Technologies Austria GmbH, Turmstrasse 44, 4031 Linz, Austria and also with the Institute of Materials Science and Technology, TU Wien, Getreidemarkt 9, 1060 Vienna, Austria. ERNST KOZESCHNIK is with the Institute of Materials Science and Technology, TU Wien and also with the MatCalc Engineering GmbH, Getreidemarkt 9, 1060 Vienna, Austria. Contact e-mail: [email protected] Manuscript submitted August 21, 2020; accepted November 6, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
to a deceleration of the rate of recrystallization, followed by an acceleration at further increasing Mg content. These results will form the basis of experimental verification
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