Shock induced plasticity and phase transition in single crystal lead by molecular dynamics simulations

Abstract

Shock-induced plasticity and phase transition in single crystal lead are investigated by nonequilibrium molecular dynamics simulations. Under dynamic shock loading, the appearance of plasticity in materials precedes that of phase transition. Plasticity mainly causes two effects: one is that plasticity has a significant relaxation effect on shear stress, and the other is that deformation twinning serves as important nucleation sites for the phase transition. This twinning is caused by mutual impediments among different cross-slips and {111} slips. There are three main stages in the dynamic phase transition process of lead: fcc → bcc-like phase transition, plasticity, and hcp phase formation and growth. Moreover, phase transition has a more significant relaxation effect on shear stress, which relaxes the shear stress to a minimum value. The spall strength of lead decreases as the shock intensity increases, but its rate of decrease under different shock intensities is different. Plasticity, especially phase transition, would obviously result in a lower rate of decrease in spall strength.