Effect of Twinning Behavior on Dynamic Recrystallization During Extrusion of AZ31 Mg Alloy

A new severe plastic deformation method, viz. integrated dual-directional extrusion and spiral deformation, was adopted to process AZ31 Mg alloy and found to be very effective for refining the grains and softening the texture. We also investigated how twinning in AZ31 alloy affected the dynamic recrystallization (DRX) during hot extrusion, revealing that multiple twins can offer increased nucleation sites and enough energy to trigger DRX. Moreover, even after dual-directional extrusion and spiral deformation, a misorientation angle of ~ 86° remained between the primary tension twin and matrix or ~ 60° between the secondary tension twin and primary twin, being induced by {10–12} tension twin variants (primary and secondary) and resulting in a dispersed misorientation angle distribution. Nucleation of DRX occurred at the tip of preexisting twins, although primary and secondary tension twins can also act as nucleation sites for DRX.