Molecular dynamics investigation of shock-induced microstructure evolution in single crystalline CoCrNi medium entropy alloy

Abstract

The atomic-scale deformation mechanisms under shock compression of single-crystal CoCrNi medium entropy alloy were investigated using molecular dynamics simulations. The anisotropic crystal properties significantly influence the elastic–plastic two-wave structure and the evolution of the microstructure. The results indicate that within the impact velocity range of 0.6–1.2 km/s, the [100] orientation exhibits a single-wave structure, although the mechanisms of plastic deformation differ. The plastic deformation of the single-crystal sample along the [100] direction is primarily governed by stacking faults and dislocation slip at lower impact velocities. However, as the shock velocity increases, the deformation mechanism transitions to a phase-transformation-mediated mode. In contrast, along the [110] and [111] directions, elastic–plastic two-wave structures are distinctly observed, accompanied by a plethora of dislocations with dislocation slip and the formation of disordered structures serving as the predominant plastic deformation mechanism.