Strengthening effects of coherent interfaces in nanoscale metallic bilayers

Dislocation nucleation and propagation in a Cu–Ni bilayer with coherent (1 1 1) interface are examined using atomistic simulations. Nanoindentation model is applied to generate dislocations at and near the surface. Mechanisms of interactions between gliding dislocations and coherent interface are investigated. It is found that the interface acts as a strong barrier to dislocation propagation, which results in considerable strengthening of the bilayer. The results are compared to indentation of pure Cu and pure Ni single crystals. It is found that the obtained maximum load for indentation of the Cu–Ni bilayer is higher than for any of the two pure materials. Strain hardening of the bilayer system due to the presence of interface is investigated by analyzing the indentation load–displacement curves.