Molecular dynamics investigation of shock front in nanocrystalline aluminum: grain boundary effects

The shock front structure and the plastic deformation of nanocrystalline aluminum under shock loading are investigated by using molecular dynamics simulations. The simulation results show that: after the elastic wave was generated, the grain boundary sliding and deformation dominated the early plastic deformation mechanisms, then the partial dislocations were nucleated at the deformed grain boundaries and spread within the grains, finally the process of stacking faults, deformation twins and full dislocation formation in the grain dominated the latter stage of the plastic deformation. The structural characteristics after the shock front swept over is that the stacking faults and the deformation twins are left in grains, and the majority of the full dislocations are annihilated at the opposite grain boundaries. It is reported for the first time that the shock front structure reflects the time sequence of two different plastic deformation mechanisms in nanocrystalline aluminum.