The size effect and plastic deformation mechanism transition in the nanolayered polycrystalline metallic multilayers

Abstract

The strength and deformation mechanisms of the nanolayered polycrystalline metallic multilayers (NPMMs) are investigated via molecular dynamics simulation, with special attentions to the coupling effect of grain size and layer thickness. The results indicate that the strength of multilayers does not always increases sensitively with the decrease of layer thickness or grain size, and the smaller one of them governs substantially the size effect on the strength. Due to the constraint of GBs and phase interface to gilding dislocations, there are several possible deformation mechanisms, which can govern the strength of NPMMs, including the confined partial dislocation slip, confined extended dislocation slip, and confined grain boundary slip. With the increase or decrease of the characteristic size of multilayers (i.e., layer thickness or grain size), the dominant deformation mechanism changes from one to another, resulting in very intricate size effect on the strength of multilayers. The underlying reason of mechanism transition and its influence on the strength is carefully discussed and analyzed in this article. © 2014 AIP Publishing LLC.