Dislocation emission and propagation under a nano-indenter in a model high entropy alloy

Abstract

The nanoindentation response of a FeNiCrCoCu high-entropy alloy is explored by means of atomistic simulations. In order to study the role of compositional complexity, we compare the behavior of the quinary FeNiCrCoCu alloy with that of an average atom potential fitted to the same overall properties of the alloy. In this way, we reveal the influence of compositional randomness of the multicomponent alloys on the onset of plasticity, deformation mechanisms and residual microstructure. Plasticity is dominated by dislocation activity, with twinning appearing as a complementary deformation mechanism in both models. While the HEA alloy substrate yields for a similar indenter penetration, indentation hardness is higher in the HEA alloy. After mitigation of strain rate effects, major differences are observed, influenced by the more difficult movement of dislocations in the compositionally complex HEA alloy. The results are in agreement with previous studies of plasticity in high entropy alloys and highlight the importance of using average atom models over comparison with single element studies for understanding complex multi principal element alloys.