Orientation-dependent ballistic response of textured Mg alloy plates: From deformation mechanisms to macroscopic fracture

α -Mg alloys inherently exhibit pronounced plastic anisotropy owing to the limited slip systems of their hexagonal close-packed lattice; this anisotropy is amplified by the crystallographic texture developed during thermomechanical processing. Despite extensive studies on quasi-static deformation, the mechanism by which such anisotropy governs the ballistic response of Mg alloys remains unresolved. This study investigated the orientation-dependent ballistic behavior of hot-rolled AZ31 Mg alloy plates with a strong basal texture by applying high-velocity impacts along the normal direction (ND) and the rolling direction (RD). The ND impact provided greater kinetic energy absorption, more pronounced bulging, and a near-circular fracture morphology, demonstrating superior ballistic impact resistance regardless of the plate thickness. Schmid factor analysis combined with microstructural characterization revealed that, under ND impact, the constant geometric relationship between the compressive loading and the basal poles enabled extensive and homogeneous extension twinning on the front surface, followed by strain-induced boundary migration and dynamic recovery on the rear surface. In contrast, RD impact introduced spatially varying angles between the compressive loading and the basal poles, promoting position-dependent activation of slip and twinning. Finite-element analysis revealed localized shear stress, concentrated plastic dissipation, and rapid strain accumulation in a specific region of the rear surface under RD impact, indicating its high susceptibility to localized adiabatic heating. These results establish a microstructure–stress–fracture correlation that links the plastic anisotropy of textured Mg alloys to their macroscopic ballistic performance.