Cryogenic incipient plasticity in bicrystalline copper with a spherical void and sigma 5 STGB by molecular dynamics simulation

Abstract

Grain Boundaries and voids are common defects in nanocrystalline metals, playing pivotal roles in plastic deformation. This study conducted molecular dynamics simulation to explore the incipient plasticity of Σ5 STGB bicrystalline Cu with a spherical void, alongside its constituent monocrystals at 10 K. The results reveal homogeneous nucleation of an elliptical 1/6<112> Shockley partial dislocation loop in the monocrystals. In the void-free Σ5 STGB bicrystal, initial dislocation nucleates homogeneously in grain interior rather than from the Σ5 STGB, forming a Shockley partial dislocation loop. In the monocrystals with a large spherical void, four initial dislocations nucleate from void surface on four slip systems. In the Σ5 STGB bicrystals with a spherical void, when the void diameter is 0.5 nm, the initial dislocation is an arc-shaped Shockley partial dislocation nucleated from the Σ5 STGB. For void diameters larger than 0.5 nm, initial dislocations nucleate from void surface. Through this study, the conditions for the nucleation, number, and morphology of initial dislocations are further understood, facilitating the evaluation of subsequent plastic deformation. This research contributes theoretical underpinnings for improving the mechanical properties and designing high-performance nanocrystalline metals.