Mechanical behavior of metallic nanowires with twin boundaries parallel to loading axis

In this paper, the mechanical behavior of Al, Ni, Cu, Au and Ag nanowires (NWs) with a coherent twin boundary parallel to their longitudinal axis was investigated using molecular dynamics simulation. Our results show that the twin-structure NWs with circular cross-section exhibited a strong twin thickness strengthening effect, which led to their yield stress continuing to increase as the twin thickness decreased. The plastic deformation mechanisms of these NWs were significantly affected by both γsf/γusf [the ratio between the stacking fault energy (γsf) and the unstable stacking fault energy (γusf)] and the twin thickness. As the twin thickness decreased to three atomic layers, we discovered two new deformation models in the NWs. For Al and Ni, their plasticity was accommodated by lattice distortion resulting in brittle-like necking. Meanwhile, for Cu, Au and Ag, their plasticity was accommodated by lattice distortion and rearrangement that led to new grain formation in the NWs.