Effect of helium bubbles on the interface shear strength of copper/niobium multilayer

Abstract

The influence of the helium bubble on the interfacial shear strength of copper/niobium multilayers and the corresponding deformation mechanisms are studied through molecular dynamics. Strong anisotropy of the shear strength is demonstrated, and the ratio of the highest strength to the lowest is approximately 4.3. The interface bubble leads to the dislocation emission under the shear along the high-strength directions and results in the severe decrease of the interface bearing capability, while the loss of the interface bearing is negligible for the case along the weak/medium-strength directions. The contradictory effects of the bubble on the interface shear strength under different shear directions are explained by the competition between the bubble-related dislocation emission and propagation and the regular uniform interface slip. For the shear along the high-strength direction, the interface could bear relatively high shear stress which is large enough to activate the dislocation from the bubble. Consequently, the corresponding deformations are dominated by the mechanism of bubble-related dislocation emission and its propagation. For the shear along the weak/medium-strength direction, the interface itself is sheared under relatively low shear stress before the effective nucleation of dislocation. Therefore, the corresponding deformation mechanism is controlled by the regular interface shear.