Interaction of dislocations with incoherent interfaces in nanoscale FCC-BCC metallic bi-layers

Dislocation nucleation and propagation in a Cu-Nb bi-layer with an incoherent face-centered cubic (FCC)-body-centered cubic (BCC) interface are examined using atomistic simulations. The nanoindentation model is applied to generate dislocations at and near the surface in one of the layers and push them through the interface into the other layer. The reasons for high strength levels in multilayered metallic composites with incoherent interfaces are investigated. The interface acts as a very strong barrier to dislocation propagation. It is found that even under severe deformation at large indentation depths, no dislocations are transmitted across the interface from Cu into Nb. While dislocation transmission from Nb to Cu can be, in general, observed, it occurs under high loading forces. In both cases, the presence of the interface results in considerable strengthening of the bi-layer. Mechanisms of interactions between gliding dislocations and the incoherent interface have been studied in detail. In particular, interface shear at the interface under complex three-dimensional loading conditions is analyzed.