Thermal deformation behavior and related deformation mechanisms of Mg–3Y alloy under shear–compression loading conditions

In this work, the shear–compression deformation behavior of Mg–3Y alloy was systematically investigated by physical and numerical simulation. During thermal deformation at 300 °C–400 °C and strain rates of 0.001s⁻¹–0.1s⁻¹, the shear–compression samples (SCSs) demonstrate sustained work hardening capability, which is supported by the Mises equivalent stress–strain curves. Numerical simulation and microstructure analysis reveal that after thermal deformation, the SCS exhibits three typical deformation regions. The slot region (Region I) is primary stress and strain concentration zone; next is the transition region (Region II); while stress and strain in the cylindrical region (Region III) are minimal. Microstructure and micro-texture analyses of the slot region indicate that at 300 °C, plastic deformation is primarily dominated by 〈a〉 basal slip, with multiple deformation twins assisting in < c >-axis deformation. At 350 °C, besides 〈a〉 basal slip, 〈a〉 prismatic slip also participates, meanwhile, the proportion of deformation twinning decreases. At 400 °C, the deformation is dominated by 〈a〉 prismatic slip, and deformation twinning nearly disappear. Additionally, both the increase in temperature and the decrease in strain rate play a promoting role in the occurrence of dynamic recrystallization (DRX). At 300 °C, twin-induced dynamic recrystallization (TDRX) occurs within gain interiors. At 350 °C, discontinuous dynamic recrystallization (DDRX) becomes the dominant mode. Both the DDRX and continuous dynamic recrystallization (CDRX) are enhanced at 400 °C. Overall, the shear–compression stresses contribute to increasing the work hardening capability, while Y solute atoms stabilize the deformation microstructure by promoting non-basal dislocation activation and strengthening inter-atomic bonding. This dual mechanism significantly impedes dislocation mobility, resulting in pronounced work hardening and a substantial delay in the progress of DRX in Mg–3Y alloy at elevated temperatures.