Molecular dynamics-based analysis of the effect of temperature and strain rate on deformation of nanocrystalline CoCrFeMnNi high-entropy alloy

Abstract

The effect of temperature and strain rates on microstructure development of a typical polycrystalline CoCrFeMnNi high-entropy alloy was conducted in the molecular dynamics study. Four typical temperatures of 77 K, 300 K, 700 K and 1100 K were selected. The results revealed that the peak stress and the flow stress decreased with the increases in formation temperatures, while the extent of twinning was found to be responsive to the temperatures. The temperature-linked differences in the growth velocity of intrinsic stacking were observed. Furthermore, three strain rates of 1 × 108 s−1, 5 × 108 s−1, and 1 × 109 s−1 were chosen to explore the influence of strain rate on the microstructural behavior of the material at 300 K. It was found that both peak stress and flow stress increased with the strain rates. The FCC → HCP phase transformation and parallel twin formation were observed as the response to plastic deformation of the material. The simulation shows that the twinning controls the inelastic deformation at low temperatures and high strain rates. With the increase in temperature and a reduction in strain rate, dislocation slipping is the main reason for the plasticity.