Strain rate dependence of twinning at 450 °C and its effect on microstructure of an extruded magnesium alloy

Deformation twinning in magnesium alloys at elevated temperatures has received relatively little attention because it is generally deemed that dislocation slip dominates plastic deformation. In this work, twinning at 450 °C in an extruded Mg–Al–Mn magnesium alloy (AM30) was studied by interrupted compression tests at various strain rates within a practical range for lab-scale extrusion (<1.0 s−1). Microstructure and texture evolution were examined by electron backscatter diffraction (EBSD) at different strain levels. The results show that sporadic twins started to appear at strain rate of 0.1 s−1, whereas profuse twinning was activated at strain rates of 0.5 and 0.8 s−1. The deformation twins quickly lost original morphology because of dynamic recrystallization. These results show that deformation twinning has a significant effect on microstructural and texture evolution of wrought Mg alloys at elevated temperatures within practical strain rate range.