Role of starting texture and deformation modes on low-temperature shear formability and shear localization of Mg-3Al-1Zn alloy

Low-temperature shear formability of Mg-3Al-1Zn (AZ31) alloy samples with two different starting textures was investigated via the equal-channel angular processing (ECAP) technique. Under careful texture modifications, the low temperature limit for the ECAP of AZ31 was reduced from the typical processing temperature of 200 °C down to 150 °C by suppressing the compression twinning activity and, instead, promoting prismatic slip. At 150 °C, with the basal poles initially parallel to the extrusion direction (ED), the sample failed during ECAP; however, it was successfully processed at the same temperature when the basal poles were perpendicular to the ED. A crystal plasticity model was used to gain a deeper understanding of operating deformation modes and dynamic recrystallization during the ECAP of different starting textures at 150 °C, the latter of which was found to play a significant role in shear localization during ECAP. Detailed electron backscatter diffraction analyses and the simulation results clearly indicate that the formation of compression twins causes deformation localization, followed by dynamic recrystallization within the compression twins at 150 °C. This non-uniform dynamic recrystallization causes local softening and large shear bands, and eventual failure during ECAP.