Effects of microstructure and temperature on the mechanical properties of nanocrystalline CoCrFeMnNi high entropy alloy under nanoscratching using molecular dynamics simulation

In this study, molecular dynamics is used to examine mechanical properties and microstructure evolution of nanocrystalline high-entropy alloy (CoCrFeMnNi) under nanoscratching load. Special attentions are paid to the effects of crystal structure, temperature, grain size and twin boundary spacing on the deformation mechanisms and microstructure evolution. The P-h curves show that the maximum indentation force is in reduced order with single-crystal, nanotwin polycrystalline and polycrystalline structures. Specifically, for the single-crystal structure, the amorphization caused by the increment of temperature hinders the movements of dislocations and stacking faults. For the polycrystalline and nanotwin polycrystalline structures, the inverse Hall–Petch relation is observed due to that the interaction between the dislocations and grain boundary (GB) / twin boundary (TB). For the nanotwin polycrystalline structure, the migration of twin boundary is observed during the process of nanoindentation. Furthermore, Hirth and Lomer-Cottrell dislocation locks, secondary twins and FCC→HCP phase transformation are also found in simulations.