Probing the microstructure and deformation mechanism of an FeCoCrNiAl0.5 high entropy alloy during nanoscratching: a combined atomistic and physical model study

Abstract

High entropy alloys (HEAs) exhibit superior mechanical properties. However, the nanoscratching properties and deformation behaviour of FeCoCrNiAl0.5 HEAs remain unknown at the nanoscale. Here, we investigate the effect of scratching depth on the microstructural and tribological characteristics of an FeCoCrNiAl0.5 HEA using molecular dynamics simulations combined with a physical model. The scratching force increases significantly as the scratching depth increases. In the lower part of the scratching region, there is a clear atomic movement process, with the load generated in the normal direction causing the atoms to shift downwards. Noticeable shear bands are formed in the subsurface area, and they are both small and narrow compared with the pure Ni. The plastic deformation mechanism of the compressed surface is mainly governed by the formation and expansion of stacking faults during the subsurface evolution process. The evolution process of screw dislocations is similar to that of edge dislocations. In addition, the high strength and deformation resistance of FeCoCrNiAl0.5 HEAs are further evaluated by establishing a microstructure-based physical model. The combined effect of the lattice distortion strengthening and dislocation strengthening promotes the high strength of the FeCoCrNiAl0.5 HEA, which is significantly better than the single strengthening mechanism of pure metals. These results accelerate the understanding of the mechanical properties and deformation mechanisms of HEAs.