Dominant Deformation Mechanisms in Mg–Zn–Ca Alloy

The coaddition of Zn and Ca has great potential to improve the ductility of Mg alloys. Herein, the mechanical properties of an extruded Mg–Zn–Ca solid-solution alloy were studied by quasi-in situ electron backscatter diffraction (EBSD)-assisted slip trace analysis. The dominant deformation mechanisms of the Mg–Zn–Ca alloy were studied, and the origins of enhanced ductility were systematically revealed. The results indicate that most grains deformed by basal slip. In addition, multiple non-basal slip traces were detected (particularly prismatic, pyramidal I , and pyramidal I slip traces), and their activation frequency was promoted with increasing tensile strain. The enhanced participation of non-basal slip systems is believed to play a critical role in achieving homogeneous plastic deformation, thus effectively promoting the ductility of the Mg–Zn–Ca alloy. Furthermore, first-principle calculations revealed that the coaddition of Zn and Ca significantly reduces the unstable stacking fault energy for non-basal slip, which contributes to the activation of non-basal slip systems during plastic deformation.