Shock response of copper bicrystals with a ∑3 asymmetric tilt grain boundary

Abstract

Molecular dynamics (MD) simulations were performed to examine the behavior of the asymmetric ∑3〈110〉(110)1/(114)2 grain boundary (GB) in copper bicrystals under shock loading, with particular regard to the GB effect on the evolution of free surface velocity, plasticity and void nucleation and growth. Shock loadings with a direction perpendicular to the GB were employed by using the typical flyer plate and target configuration at three different velocities of 0.375, 0.5 and 0.75km/s. Our results showed that due to the existence of the GB, the free surface velocity of copper bicrystal exhibited an inclined plastic plateau in its historical curve when compared to the monocrystal. Shock front of bicrystal was found to become wider than that of the monocrystal since GB plasticity was triggered when the elastic wave crossed the GB. Spall strength also was lower in bicrystal than monocrystal loading at the same impact velocity. GB sliding and grain rotation under the shock wave were also observed, which induced the 180° phase shift of Vy, the relaxation of shear stress and the increase of temperature at the GB region. It was also found that due to the weakening effect of GB and the stress concentration, voids tend to nucleate and grow along the GB.