Atomistic simulation of nanoindentation on incipient plasticity and dislocation evolution in γ/γ′ phase with interface and void

Abstract

Nanoindentation of γ/γ′ phase in Ni-based single crystal alloy is simulated by the molecular dynamics method. The perfect γ/γ′ phase model and the defective model with a void in the γ phase are researched respectively. Center-symmetry parameter is used to analyze the incipient plasticity and the dislocation evolution during the nanoindentation process. The results show that the incipient plasticity begins with the nucleation of dislocations in both two models. However, there are some different phenomena between the two models. Firstly, the elasticity stage of the defective model is much shorter than the perfect model since the presence of a void and the decrease of indentation load in the defective model is much more conspicuous. Secondly, the nucleation of new dislocations in the defective model is later than in the perfect model as the collapse of the void consumes the accumulated strain energy. Moreover, the stacking faults form at the indentation depth 1.32nm in the perfect model while no stacking faults are found at the same indentation depth in the defective model. At last, none of dislocations moves into the γ′ phase because of the existence of the misfit dislocations in the γ/γ′ phase interface in both models. The dislocations tangle around the void in the defective model when the indentation depth arrives 1.6891nm, which causes a lower indentation load contrasting to the load of the perfect model at the same depth.