Effect of Grain Size on Dynamic Compression Behavior and Deformation Mechanism of ZK60 Magnesium Alloy

Abstract

The dynamic compression deformation of 3 µm, 15 µm and 25 µm grain size ZK60 alloys under high-strain-rate compression is systematically studied. Dynamic compression experiments at a strain rate of 1700 s−1 were conducted using a split Hopkinson pressure bar, and the microstructure of the specimen was characterized via electron backscatter diffraction and transmission electron microscopy, as well as via the calculation of Schmid factors. The results showed that the alloy exhibited the decrease in yield strength and peak stress as the grain size increased under dynamic compression. The grain refinement in the alloy was conducive to the activation of basic slip. In turn, an increase in the grain size caused the transition in the main deformation mechanism from pyramidal <a> slip to {10−12} tensile twinning and pyramidal <a> slip. Based on these deformation mechanisms, the Johnson-Cook constitutive equation with different grain sizes was modified, and the fitting results were in accordance with the experimental data.