Molecular dynamics simulation of deformation mechanism of CoCrNi medium entropy alloy during nanoscratching

While material design and mechanical properties have been extensively investigated in medium entropy alloy (MEA), resources are no available to evaluate more complex mechanical behaviors such as friction and wear. Here, the unique deformation mechanism of CoCrNi MEA during nanoscratching has been explored in depth at a qualitative level by molecular dynamics simulation. The characteristics of dislocation reaction and evolution during nanoscratching are emphasized and compared with pure nickel. We find that the typical defect structures are formed in multi-principal element alloys rather than in pure metals. The calculation of the shear stress component provides a reasonable explanation for the generation of defects in MEA. In particular, the focus is on the generation and evolution of the distorted prismatic dislocation loop in the compression region, as well as phase-transformations and nanotwins promoted in the tensile region. Moreover, we explain the work hardening and load drop events during nanoscratching by the analysis of dislocation evolution. The objective of this contribution is to provide a computational study incorporating defect theories to gain insight into the deformation mechanism of MEA under tribological loads, thereby facilitating the development of new MEAs with excellent tribological performance.