Evaluation of Twinning Behavior in Rolling of Mg Alloys with Three Kinds of Textures by a Generalized Schmid Factor
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Evaluation of Twinning Behavior in Rolling of Mg Alloys with Three Kinds of Textures by a Generalized Schmid Factor Changfa Guo1,2 · Yue Xiao1 · Renlong Xin1,3 Received: 3 April 2019 / Accepted: 14 July 2019 © The Korean Institute of Metals and Materials 2019
Abstract In this work, we statistically investigate the texture effect on twinning behavior in rolling of an AZ31 Mg alloy by electron backscatter diffraction technique and evaluate it by a generalized Schmid factor (GSF). The results show that twinning nucleation and area fraction are promoted significantly with the c-axis of grains rotating from the transverse direction to the rolling direction. More importantly, twin propensity and the selection of twin variants can be well explained by the GSF that is calculated based on an estimated stress state for rolling. The present results provide some insights into controlling the microstructure and texture of Mg alloys by rolling processes. Keywords Generalized Schmid factor · Twinning · Variant selection · Magnesium alloy
1 Introduction In order to achieve optimal strength and toughness, various plastic processes have been employed to tailor the microstructure and texture of wrought Mg alloys in recent years [1–5]. Among them, rolling was frequently used featuring a complex stress state and high deformation rate [5–8]. For hexagonal close packed metals, deformation twinning is a very important deformation mechanism. Therefore, extensive work has been done on twinning mechanisms in Mg alloys [9–11]. It was found that profuse twinning can be introduced in Mg alloys by pre-rolling to tailor the microstructure and hence improve the mechanical properties [6–8]. In order to better optimize the microstructure via
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12540-019-00378-0) contains supplementary material, which is available to authorized users. * Renlong Xin [email protected] 1
Joint International Laboratory for Light Alloys (MOE), College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
2
College of Mechanical and Electrical Engineering, Jiaxing University, Jiaxing 314001, China
3
State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China
twinning, it is necessary to understand in depth the twinning behavior during rolling deformation on Mg alloys. To study the variant selection of twins formed in rolling deformation, the classic Schmid law has been employed considering only the compressive stress along the normal direction [12]. In order to interpret some anomalous twins in rolling or plane strain compression (PSC), a lateral stress was also considered, which has a value of one half or third of that along the normal direction. Accordingly, a modified Schmid factor (MSF) was used to assess twinning behavior [13–16]. However, the validity of the MSF for the selection of twin variants by statistical analysis is rare. In addition, a strain accommodation concept has been used to
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