Atomistic simulations of the nanoindentation-induced incipient
plasticity in Ni3Al crystal

Kai Xiong, Haiming Lu, Jianfeng Gu

Keywords: Nanoindentation, Dislocations, Atomistic modeling, Nickel based superalloys

Abstract: In this work, the indentation-induced incipient plasticity of Ni3Al crystal is investigated by performing molecular dynamics (MD) simulations. Simulation results reveal that the incipient plasticity of Ni3Al is originated from the homogeneous nucleation of the 1/6h112i-type Shockley partial dislocation. The critical load, critical contact pressure, dislocation nucleation site and active slip system are significantly affected by crystallographic orientation, model size, indenter radius and temperature. The choice of interatomic potential has significant implications for the indentation behavior of Ni3Al. Some benchmarks for evaluating the credibility of interatomic potentials are presented. The pop-in phenomena are correlated with dislocation generation, multiplication and reactions. The formation mechanisms of complex stacking faults (CSFs), antiphase boundaries (APBs) and superlattice intrinsic stacking faults (SISFs) are clarified. The highest indentation modulus is obtained in (111) indentation followed by the (110) and (100) cases. The indentation modulus and the depth of nucleation sites increase with increasing indenter radius but the maximum shear stress decreases. The maximum shear stress and indentation modulus decrease linearly with increasing temperature, reflecting the stress-assisted and thermally activated nature of dislocation nucleation.