Effects of orientation and vacancy defects on the shock Hugoniot behavior and spallation of single-crystal copper

The effect of crystal orientation on the dynamic response of single-crystal copper is explored by using a molecular dynamics method with a realistic embedded atom potential. Three crystallographic orientations ([1 0 0], [1 1 0] and [1 1 1]) along which the shock waves propagate are investigated. For each orientation, an initial vacancy concentration (C-v) ranging from 0% to 2% is introduced to also take the effect of vacancy defects into consideration. The simulations characterize the defective Cu system in terms of shock Hugoniot behavior, local microstructure evolution and spall strength during the shock wave propagation. The shock wave is applied by pulling a layer of piston atoms at a velocity of 0.25-2 km s(-1) with the Hugoniot pressure ranging from 15 to 120 GPa. The simulation results show that shock responses and the role of vacancy defects are strongly anisotropic for the three orientations investigated. For shock along the [1 0 0] orientation, vacancy defects have a negligible effect on the shock Hugoniot curve u(s)-u(p) relationship, but play a role in increasing spall damage. In contrast, for shock along the [1 1 0] and [1 1 1] orientations, vacancy defects not only significantly reduce the anisotropic level of u(s)-u(p) relationships, but also significantly decrease spall damage. Based on this, the orientation-dependent effects of vacancy defects on spallation strength and spall damage are analyzed by examining the defective evolution of single-crystal copper microstructure.