Plastic deformations in NiCoFe medium-entropy alloy investigated using nanoindentation simulations

• The deformation mechanism of NiCoFe medium-entropy alloy was investigated using nanoindentation simulations. • Nanoindentation-induced defects were analyzed including dislocations, stacking faults, nanotwins, and hcp phase. • The deformation mechanism exhibited orientation dependence, and the [111] plane surface showed the highest Young’s modulus. Medium-entropy alloys (MEA) have potential load-bearing applications as high-performance structural materials. In this work, the plastic deformations in NiCoFe MEAs were investigated using nanoindentation atomistic simulations. The nanoindentation responses of three typical orientations of NiCoFe single-crystals were investigated, i.e., [001], [011] and [111]. The results show that, during nanoindentation, Shockley partials on (111) slip planes remarkably affect dislocation-related activities including nucleation, gliding, and interactions. The form of atomic pile-ups is highly non-uniform and strongly asymmetrical due to the presence of multi-principal elements. The dislocation nucleation mechanism of the alloys during nanoindentation is proposed in detail. We find evidence that a hexagonal close-packed phase is formed from the face-centered cubic structure during nanoindentation.