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

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.