Investigation of the twin-induced adiabatic shear bands evolution in a Mg-Al-Mn alloy under ballistic impact

The formation and evolution of twin-induced adiabatic shear bands (ASBs) in a Mg-Al-Mn alloy under ballistic impact were investigated by analyzing the microstructures at three representative locations with different distances from the crater rim. Results show that localized shear deformation occurred at the twin boundaries, resulting in the formation of ASBs. The ASBs thicken at the expense of the deformation twins with increasing plastic deformation, forming ASBs which are mainly composed of subgrains, ultra-fine recrystallized grains and Mg17Al12 precipitates. The appearance of the twin-induced ASBs is mainly attributed to the twin-twin intersections caused by high strain rate deformation. The twin-twin intersections under high strain rate deformation lead to a different twinning activity in which the subsequent plastic deformation mainly occurs by shear deformation along the twin boundaries rather than thickening the twins. These results and analysis can shed new light on understanding the nucleation and evolution of ASBs in Mg alloys under dynamic loadings.