Quasi-in situ observation of extension twinning of AZ31 magnesium alloy under co-directional dynamic compression

In this paper, twinning nucleation and microstructure evolution of AZ31 magnesium alloy were investigated during the quasi-in situ dynamic compression. The microstructure characterization of the sample before and after deformation was performed via electron backscatter diffraction and transmission electron microscopy. The strain accommodation was estimated by selecting twinning variants and using the geometric compatibility factor (m'). The nucleation behavior of 55.4% extension twinning obeyed Schmid's law under high strain rate compression. The non-Schmidt twinning variants with the highest geometric compatibility factor (m') in the active twinning system of adjacent grains were activated in paired twins that affected the twining nucleation and variant selections.