Microstructural evolution of single-crystal magnesium under elevated temperature and ultra-high strain rate

Abstract

Despite numerous studies of the deformation behavior of magnesium (Mg), its microstructural evolution at different temperatures and strain rates remains largely unexplored. In this paper, the evolution of dislocations and amorphous regions in single-crystal Mg under compressive loading along the c-axis is investigated using molecular dynamics simulations, and temperature and strain-rate dependence of the microstructural evolution is revealed. At a strain rate of 107 s-1, the dislocations are low in density, and they slip and evolve unevenly as the strain in the single crystal increases. Consequently, the stress in the single crystal varies in a zigzag manner with increasing strain. The dislocation density is higher at strain rates of 108 s-1 and 109 s-1, resulting in relatively smooth deformation and stress-strain curves. At a strain rate of 1010 s-1, the amorphous regions achieve a very high fraction during deformation, contributing to softening and smoother deformation of the single crystal. The fraction of amorphous regions also increases with increasing temperature, which is an important cause of the temperature softening effect. Furthermore, the initiation of dislocations and amorphous regions is also studied at different strain rates and temperatures.