In this research, the dynamic compression behaviour of 5 and 1.5 µm grain size samples of Mg–4Zn–1Y alloy was investigated by the split Hopkinson pressure bar at the strain rate of 1000–1700 s−1. The microstructure, texture evolution, and the deformation mechanisms of samples were characterised by electron backscattering diffraction. The result showed that the grain refinement caused tension twining, which resulted in the distinct true stress–strain curves with specific grain sizes. It was found that the pyramidal < c + a > and pyramidal <a > slips were the main deformation mechanisms of 5 and 1.5 µm samples under dynamic compression, respectively. The constitutive modelling of Mg–4Zn–1Y with different grain sizes was also developed by introducing the grain size adjustment parameters.

The effect of grain size on the adiabatic shear behaviour of AZ31 Mg alloy under high-strain-rate deformation was investigated in the present study. Samples with three types of grain sizes were prepared, and the hat-shaped samples were subjected to the high-strain-rate deformation. The high-strain-rate deformation was conducted at 1600 s–1 by using a split Hopkinson pressure bar at 200°C. The microstructure before and after deformation was observed by optical microscopy and electron backscatter diffraction. The results indicated that the adiabatic shear sensitivity increased with the increase in the grain size. The calculation results indicated that the dynamic recrystallisation grains in the adiabatic shear band were formed by rotational dynamic recrystallisation.

The formation of adiabatic shear band (ASB) and its damage behaviour in AZ31 alloy under high strain rate compression (2000 s−1) were investigated in this study by using a split Hopkinson pressure bar. Microstructure of the ASB was characterised by electron back-scattering diffraction and transmission electron microscopy, and the adiabatic shear damage behaviour was analysed through finite element simulation by LS-DYNA. The results show that the ASB and the surrounding microstructure form a gradient microstructure distribution, and the formation of ultra-fine grains in the ASB is due to rotational dynamic recrystallisation. The combination of work hardening and grain refinement in ASB leads to a high microhardness. Micro-voids grow in the ASB and eventually form macro-cracks, leading to material failure.

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