Hardening due to Interfacial He Bubbles in Nanolayered Composites

A series of helium (He) implantations with varying energies and doses were used to introduce bubbles into interfaces in Cu/Mo, Cu/V and Cu/Nb nanolayered composites. Micro-pillar compression testing revealed that the interfacial He bubbles give rise to modest hardening as compared to those in grain interiors. The flow stress enhancement is proportional to the strength of the un-implanted sample. We discuss the influence of the structure of the interfacial dislocation network, the shear resistance of the interfaces, and atomic-level interface steps on hardening. Interfaces with higher density of misfit dislocation intersections and lower shear resistance tend to provide greater hardening.