Effects of pretwins on texture and microstructural evolutions of AZ31 magnesium alloy during high temperature deformation

In this work, the effects of pretwins on the flow behavior, microstructure, and texture evolution of a rolled AZ31 magnesium alloy during hot deformation along three different orthogonal directions were studied via compression tests conducted at 25–350 °C. The flow behavior along different directions was discussed based on the operation of different deformation mechanisms in twinned and untwinned regions. Detwinning was the dominant deformation mechanism during compression in the normal direction at low temperatures, but ceased as the temperature increased to 250 °C. In the latter condition, the effect of pretwins on the texture reorientation led to a decrease in the yield strength. Pretwins stimulate the microstructure condition preceding dynamic recrystallization (DRX) during the compression of samples along the rolling and transverse directions, leading to lower peak strains. The results showed that the pretwins increased the grain size and fraction of DRX at 250 °C. The greatest increase in the DRX fraction was obtained for deformation parallel to the normal direction. The effect of pretwins on the grain boundary characteristics of the samples deformed along the normal direction was investigated. The pretwinned samples showed more significant texture rotation for dynamically recrystallized grains compared with parent grains during deformation parallel to the normal direction.