Effect of void morphology on void facilitated plasticity in irradiated Cu/Nb metallic nanolayered composites

Voids are common radiation-induced defects in nuclear materials and produce detrimental effects on mechanical properties. The influence of a pre-existing void on mechanical behavior has been investigated in single crystals, but the effects of void located at bimetal interfaces on the dislocation nucleation mechanisms and associated mechanical performance have not been fully studied. Using Cu/Nb metallic nanolayered composites (MNCs) as a model system, with atomic-scale simulations, we report on the influence of a pre-existing void at the Cu/Nb interface on dislocation nucleation and deformation behavior. Compared with the void-free system, the size, location and shape of the voids can influence dislocation behavior significantly, such as the initial nucleation site, the critical nucleation stress, and the preferred slip system. As the size of the faceted void increases from 3 to 4 nm, the dominant mechanism of dislocation nucleation changes from a misfit dislocation-assisted localized shear to a void edge-assisted Frank-Read-like mechanism. Also, the location of the faceted void can change the coupled strain field between the void and the misfit dislocation, ultimately affecting the preferred slip system selection. In contrast, the spherical void cannot effectively activate the Frank-Read-like dislocation source due to the absence of edges. This work reveals the effects of void morphology on dislocation behavior, and provides an explanation for co-dominated plasticity of bimetal interface and void.