The slip behaviour in coherent and semi-coherent metallic bilayer composites was examined by atomic simulation of the Cu/Ni and Cu/Ag systems. The coherent interface in Cu/Ni, although energetically unfavourable relative to the semi-coherent interface in thick layers, exhibited several interesting behaviours. Linear elastic predictions of the lattice strains required to achieve coherency (remove the 2.7% lattice mismatch) were found not to satisfy equilibrium. The reason was a non-linearity of the elastic response. Application of the stresses required for glide dislocations to cross the interface, or to escape from the interface, increased the non-linearities in the elastic response of the system. Koehler forces, arising from elastic mismatch, were observed in some cases to have the wrong sign relative to linear-elastic predictions. The core structures of misfit dislocations in semi-coherent interfaces were observed to be quite different in the cube-on-cube oriented Cu/Ni and Cu/Ag systems with interfaces parallel to (010). In the former case, the (a/2)<110> misfit dislocations had very narrow cores in the plane of the interface, but dissociated into Lomer-Cottrell locks out of the interface on the Cu side. This dissociation was enhanced by the application of tensile stresses, and could lead to reactions that formed continuous stacking-fault structures. Such structures were shown to be strong barriers to slip. The stabilities of such structures were analysed and, within the approximations used, it was found that such structures could be more stable than the usual 2-dimensional flat grid of misfit dislocations. On the other hand, the misfit dislocations at Cu/Ag interfaces were wide and therefore fairly mobile in the interface plane.

On the Strengthening Effects of Interfaces in Multilayer FCC Metallic Composites. R.G.Hoagland, T.E.Mitchell, J.P.Hirth, H.Kung: Philosophical Magazine A, 2002, 82[4], 643-64