Modeling twinning, detwinning, and dynamic recrystallization of magnesium alloys
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oduction Due to their low density, high-specific strength, and stiffness, magnesium (Mg) alloys present a good solution to the increasing demand for lightweight, energy saving, and environmentally friendly engineering systems. Because of their hexagonal close-packed (hcp) crystal structure, Mg alloys show more complex mechanical behavior than other metallic alloys, especially those that are widely available and currently in use.1,2 Depending on loading conditions such as temperature and strain rate, various deformation mechanisms, including slip, twinning, detwinning, and dynamic recrystallization (DRX), participate to accommodate strain in Mg alloys. At ambient temperature, in addition to easy basal slip, the alternative mechanisms available are nonbasal slip and tensile twinning.3,4 The threshold resistance for nonbasal slip is much higher than that for basal slip, hence tensile twinning, whose threshold resistance is close to that of basal slip, becomes an important deformation mechanism
for Mg alloys. The hcp structure and twinning activity lead to the characteristic basal texture of wrought Mg alloys, the strong anisotropic ductility and strength, the tension/ compression asymmetric stress–strain behavior, and the limited formability at ambient temperature.5 Upon load reversal during complex loading, detwinning, which is another deformation mechanism, can also occur at room temperature. The alternating twinning and detwinning lead to asymmetric hysteresis stress–strain loops under cyclic loading or lowered yield strength during loading direction change,6,7 which complicates the understanding and modeling of the mechanical behavior of these alloys. Hot forming is usually employed for Mg alloy processing because of the improved formability of these alloys at elevated temperatures. A higher temperature generally leads to a lower flow stress, higher ductility/formability, and weaker tension/compression asymmetry,8–10 which are a result of DRX, nonbasal slip,11–13 and the suppression of twinning.
Huamiao Wang, School of Mechanical Engineering, Shanghai Jiao Tong University, China; [email protected] Shuangming Li, Northwestern Polytechnical University, China; [email protected] Dayong Li, School of Mechanical Engineering, Shanghai Jiao Tong University, China; [email protected] Gwénaëlle Proust, School of Civil Engineering, The University of Sydney, Australia; [email protected] Yixiang Gan, School of Civil Engineering, The University of Sydney, Australia; [email protected] Kun Yan, The University of Manchester, UK; [email protected] Ding Tang, School of Mechanical Engineering, Shanghai Jiao Tong University, China; [email protected] Peidong Wu, Department of Mechanical Engineering, McMaster University, Canada; [email protected] Yinghong Peng, School of Materials Science and Engineering, and School of Mechanical Engineering, Shanghai Jiao Tong University, China; [email protected] doi:10.1557/mrs.2019.254
© 2019 Materials Research Society MRS BULLETIN VOLUME 44 • NOVEMBER 2019o
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