Strengthening effects of various grain boundaries with nano-spacing as barriers of dislocation motion from molecular dynamics simulations

Abstract

Strengthening in metals is traditionally achieved through the controlled creation of various grain boundaries (GBs), such as low-angle GBs, high-angle GBs, and twin boundaries (TBs). In the present study, a series of large-scale molecular dynamics simulations with spherical nanoindentation and carefully designed model were conducted to investigate and compare the strengthening effects of various GBs with nano-spacing as barriers of dislocation motion. Simulation results showed that high-angle twist GBs and TBs are similar barriers and low-angle twist GBs are less effective in obstructing dislocation motion. Corresponding atomistic mechanisms were also given. At a certain indentation depth, dislocation transmission and dislocation nucleation from the other side of boundaries were observed for low-angle twist GBs, whereas dislocations were completely blocked by high-angle twist GBs and TBs at the same indentation depth. The current findings should provide insights for comprehensive understanding of the strengthening effects of various GBs at nanoscale.