Investigation of the elastically shock-compressed region and elastic–plastic shock transition in single-crystalline copper to understand the dislocation nucleation mechanism under shock compression

Abstract

Shock-induced plasticity in FCC crystals has been demonstrated in many experimental and numerical simulation studies. Even though some theories have been proposed with regard to dislocation nucleation, the phenomenon occurring in the elastically shock-compressed region and the elastic–plastic transition region, which might be the origin region for dislocation nucleation, is largely unexplored. In this work, we present a molecular dynamics simulation of the shock compression of a Cu single crystal along the 〈110〉 direction specifically focusing on the mechanisms observed in the elastically compressed and the elastic–plastic transition regions. A distribution of planes of high and low atomic volume is observed in the elastically compressed region near the shock front, but the distribution becomes random as the elastic–plastic transition regime is approached. Density variations are also observed. It is observed that the formation of the defects initiates through local atomic shuffling/rearrangement. Shear stress distribution shows values greater than those required for homogeneous nucleation, and Shockley partials are observed at a certain region behind the shock front. Potential energy variations are also observed in these regions, explaining the mechanisms leading to dislocation nucleation. The present findings shed new insight into the mechanism of dislocation nucleation in shock-induced single-crystal FCC metals.