Role of prismatic a dislocations in sub-zero temperature deformation of Mg-Gd-Y-Zr alloy

This work investigates the effect of activating and accumulating prismatic < a > dislocations on ductility of a Mg-7.37Gd-3.1Y-0.27Zr (GW83K) alloy at sub-zero temperatures. It is found that the prismatic < a > dislocations were more easily activated with decreasing temperature due to the lowering of CRSS prismatic < a > /CRSS basal < a > ratio in this alloy. Increasing the proportion of prismatic < a > dislocations shows limited effect on improving the ductility of GW83K alloy in the early-stage deformation at sub-zero temperatures, because the prismatic < a > dislocations cannot accommodate c-axis deformation. However, with the formation of low-angle grain boundaries rotating along [0001] axis induced by the accumulation of prismatic < a > dislocations, the GW83K alloy can perform a much better ductility in the late-stage deformation. Such a finding provides a new perspective on understanding the contribution of prismatic < a > dislocations to ductility in Mg alloys.