Interaction Between Nano-Voids and Migrating Grain Boundary by Molecular Dynamics Simulation
42 Pages Posted: 4 Apr 2019 First Look: Accepted
Understanding the interaction between void and grain boundary (GB) is of great importance to the design of radiation resistant materials by GB engineering and to achieve high quality solid-state sintering and metallurgical diffusion joining. In this study, the interaction between nano-voids and GBs has been systematically investigated by molecular dynamics simulations. The bicrystal Cu sample was used throughout the work, and the effect of GB structure, void size, and temperature on the simulation results was considered. Both high-angle GBs(Σ5(310)GB, Σ5(210)GB) and low-angle GBs (Σ37(750)GB, Σ61(650)GB) were examined, and the dynamic GB-void interaction was realized by GB migration under constant shear deformation. The transition of the deformation mechanism from GB migration to dislocation propagation was observed during the interaction between voids and high-angle GBs at low temperature (T=10 K). At higher temperature (T=300 and 600 K), the effect of voids on GB motion depends on both temperature and void size. The migrating GB can be pinned at voids, freely traversed voids, or absorbed voids during their interaction. The void-drag effect on GB motion was analyzed based on the Zener-like equation, which implies that the retarding pressure applied to the migrating GB by a void is closely related to the surface area of the void, the degree of contact between GB and void, and GB energy. By investigating the thermal stability of a void at the static GB, it was found that the dissolution of voids at a migrating GB cannot be attributed solely to the thermal diffusion mechanism, the moving boundary can significantly reduce the time of GB atoms filling up the void. The low-angle GBs show less ability to remove the voids than the high-angle GBs, which can be ascribed to its discrete boundary structure and the lower boundary energy.
Keywords: Molecular dynamics, Grain boundary, Dislocation nucleation, Void-drag
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