Shock melting of single crystal copper with a nanovoid: Molecular dynamics simulations

We investigate the effects of nanovoid on the shock melting of single crystal Cu using molecular dynamics simulations. The properties of the void collapsed region evolving with time are characterized by order parameter, mean-squared displacement, radial distribution function, and local temperature. It is shown that prior to homogeneous melting of bulk solid, heterogeneous local melting in the void collapsed region dominates the melting process. As the hot spot formed during void collapse cools, we observe that the melting zone will recrystallize for some lower piston velocities (2.75, 3.0, and 3.1 km/s), and the recrystallization time reduces with decreased shock intensities. For higher piston velocities (3.2 and 3.3 km/s), the melting zone retains liquid state and grows slowly with time while the other part of the shocked region retains solid. It is also found that the local melting of the void collapsed region undergoes certain degrees of superheating lower than that of the perfect crystal under shock loadings.