Molecular dynamics studies on the interface evolution characteristics and deformation mechanisms of Cu/Al multilayers during compression process

The interface evolution characteristics and deformation mechanisms of Cu/Al multilayers are investigated via systematic molecular dynamics simulations. It is found that both the yield strength and ductility increase slightly with increasing strain rate, and the stress-strain curves exhibit two main yield points for all strain rate loadings. The first yield point correlates with the decomposition of perfect misfit dislocations on the interface and the propagation of partial dislocations inside the Al layer, and the second yield point relates with the dislocation transmission from the Al layer into the Cu layer. The lower the loading strain rate, the more severe the fluctuations on the stress-strain curve. However, the strain rates do not change the evolution way of dislocation networks. The calculated evolution curves of dislocation numbers indicate that the dislocation density inside the Cu layer is lower than that inside the Al layer. The interface region displays a serrated structure without voids or cracks, and the higher the loading strain rate, the more serious the interface roughening deformation. The main deformation mechanisms, respectively, are the formation of a lamellar twin structure in the Cu layer and dislocation slip in the Al layer, and the interface roughening is mainly dominated by the formation of a lamellar twin structure. Furthermore, the deformation mechanisms do not depend on the strain rate applied in this paper. In addition, we also discuss the growth curve of interface thickness which is divided into three stages.