Deformation mechanisms and differential work hardening behavior of AZ31 magnesium alloy during biaxial deformation

Magnesium alloys are frequently subjected to biaxial stress during manufacturing process, however, the work hardening behavior under such circumstance are not well understood. In this study, the deformation mechanisms and differential work hardening behavior of rolled AZ31 magnesium alloy sheets under biaxial loading are investigated. The change of plastic work contours with increasing plastic strain indicates the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state, resulting in higher macroscopic work hardening rates of biaxial loading than uniaxial loading, with the elastic-plastic transition part of work hardening extended and stage III hardly emerged. Electron backscatter diffraction and Schmid factor analysis confirm the low activation of non-basal 〈a〉 slip during biaxial loading tests. While the thickness strain is primarily accommodated by pyramidal 〈c + a〉 slip at the initial stage of biaxial deformation, {10–11} contraction twinning is activated at larger plastic strain. The low activation of non-basal 〈a〉 slip also retards the dynamic recovery and cross-slip of basal and prismatic 〈a〉 slips, leading to the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state.