{10(1)over-bar2} twins in the rolled Mg-Zn-Ca alloy with high formability

Hot-rolled Mg-Zn-Ca alloy, followed by annealing, shows high formability at room temperature because of the reduced intensity of the basal texture. [Y. Chino et al., Mater. Trans. 51, 818 (2010).] In the present work, microstructures of the as-rolled Mg-Zn-Ca alloy were investigated using electron backscattered secondary diffraction and transmission electron microscopy. In addition, first-principles calculations were performed to investigate the twinnability of the Mg-Zn-Ca alloy. The microstructural investigations revealed that fine {10 (1) over bar2} twins and local fine-grained microstructures were formed. It is therefore suggested that the fine twins induce this local fine-grained microstructure, which become the nuclei for recrystallization during annealing. As a result, the intensity of the basal texture is reduced. Calculations revealed that the {10 (1) over bar2} twinnability is enhanced by the addition of Ca because of the increased unstable stacking fault energy (gamma(us)) and decreased unstable twin fault energy (gamma(ut)).