Modulation period dependent mechanical properties of Cu/Fe metallic multilayered films

We performed molecular dynamics simulations for uniaxial tension of Cu/Fe nano-multilayered films with different modulation periods (λ) using Kurdjumov-Sachs (K-S) relationship to investigate their interfacial morphologies and the effects of λ on their mechanical properties. It shows that the mismatch dislocation lines at the interfaces are periodic. At the Cu side of the interface, triangles distribute with the smallest period; while at the Fe side, parallelograms distribute with the smallest period. There are two yield points, except the case of λ=2.10 nm where there is only one yield point, in the stress-strain curve of Cu/Fe multilayer film under tension, corresponding to the sequential nucleation of dislocations in the Cu and Fe layers from interface, respectively. We further found that there is a critical modulation period, λc, and the flow stress decreases with the increases of λ if λ > λc while increases with the increases of λ if λ < λc. The possible mechanisms are discussed.