Microstructural mechanisms of initiation of adiabatic shear failure in fine-grained Mg–4Zn–1Y alloy under dynamic loading

This study systematically analyzes the microstructural mechanisms underlying the initiation of failure in fine-grained Mg–4Zn–1Y alloy under dynamic loading. Fine-grained Mg–4Zn–1Y alloy specimens were prepared using equal-channel angular pressing (ECAP), followed by dynamic compression testing. The deformation microstructure was characterized using optical microscopy (OM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results show that, at a deformation temperature of 200°Cand a strain rate of 1200 s −1 , narrow adiabatic shear bands (ASBs) form during shear deformation, consisting of dispersed fine dynamically recrystallized (DRX) grains. Microvoids and microcracks are distributed along the shear direction within the ASBs. In non-ASB regions, high-density twins dominate, and twinning-induced grain orientation adjustment facilitates the activation of slip systems, providing conditions for strain localization. Within the ASBs, twinning-induced dynamic recrystallization (TDRX) and discontinuous dynamic recrystallization (DDRX) act synergistically, driving grain refinement and recrystallized microstructure formation, marking the onset of adiabatic shear failure.