Multiscale simulations using the quasi-continuum method with the embedded-atom method potential were performed in order to examine the mechanical response of Cu–Ag bilayer film during nano-indentation tests. An attempt was made, from the viewpoint of collective interaction among misfit dislocations on the interface, to account for the strengthening and weakening mechanisms of interface on Cu–Ag bilayer film. The details of misfit dislocation nucleation, motion and collective interaction on Cu/Ag and Ag/Cu interfaces were considered systematically, respectively. The investigation showed that the property and performance of Cu–Ag bilayer film mainly depend on the mechanical property of upper film. Both the strengthening and weakening effects were closely related to the collective interaction among misfit dislocations on the interface. Due to the pinning effect of interface on misfit dislocation, both the local interface migration and the voids could be observed at the core region of misfit dislocations. For nano-indentation on Cu/Ag bilayer film, the plastic deformation was localized chiefly in the lower Ag substrate and the void will disappear with the redistribution of misfit dislocations, which indicate that there were distinct protective and strengthening effects of the upper Cu film on the lower Ag substrate. While, for nano-indentation on Ag/Cu bilayer film, both the upper Ag film and the lower Cu substrate experience plastic deformation and the voids will not disappear, which imply that there were an obvious weakening effect of the upper Ag film on the lower Cu substrate. In addition, the multiscale simulation results were consistent with the experimental results.

Quasicontinuum Study the Influence of Misfit Dislocation Interactions on Nanoindentation. J.Li, H.Lu, Y.Ni, J.Mei: Computational Materials Science, 2011, 50[11], 3162-70