Molecular dynamics simulation of dislocation behavior during nanoindentation on a bicrystal with a Σ = 5 (210) grain boundary

Molecular dynamics simulation of nanoindentation was performed to investigate dislocation interaction with a grain boundary. A nickel single crystal and a nickel bicrystal with a vertical Σ = 5 (210) grain boundary were constructed for indentation simulation using a diamond indenter. An embedded atom potential for Ni was used for simulation and the interaction between nickel substrate and diamond indenter was set to have a fully repulsive force to emulate a traction free surface. Results showed that the indentation nucleated dislocations in the shape of prismatic loops and they propagated along the slip system of FCC crystals. The dislocation loops were composed of two sets of parallel stacking faults bound by two Shockley partial dislocations. In the case of indentation on the bicrystal, propagating dislocation loops merged into the grain boundary and induced the lateral grain boundary migration. Analysis of atom movement during the indentation suggested that the grain boundary migration was caused by the interactions of the lattice dislocations with grain boundary dislocations, resulting in cooperative atom motions near the grain boundary.