Highly localized shear deformation in a Mg–Al–Mn alloy subjected to ballistic impact

Shear localization, which might result in the formation of shear bands in materials, is considered as a dominating deformation mechanism in materials under dynamic loading. In the present study, the microstructures of twin-induced ASBs in a Mg–Al–Mn alloy under ballistic impact were studied using scanning electron microscope and transmission electron microscope to investigate the localized shear deformation behavior of Mg alloys under high strain rate deformation. The results show that highly localized shear deformation mainly occurs at the boundary regions of deformed twins, resulting in the formation of narrow shear bands. The twin-induced ASBs composed of fine recrystallized grains and Mg₁₇Al₁₂ precipitates, while the internal part of twins shows the microstructure with elongated grains. The initiation of ASBs at the twin boundary regions is mainly attributed to the stress concentration at twin boundaries due to the dislocation pile-up. These results can contribute to further understanding of the shear deformation behavior of Mg alloys under dynamic loading.