Strain softening observed during nanoindentation of Equimolar-Ratio Co-Mn-Fe-Cr-Ni High Entropy Alloy

This research article presents an atomistic study on the cyclic nanoindentation of equimolarratio Co-Mn-Fe-Cr-Ni high entropy alloy (HEA) using molecular dynamics simulation. The study investigated the effects of indentation depth on the cyclic load vs. indentation depth of the HEA. The results showed that the cyclic response exhibits a pronounced shift towards plasticity with pile-up formation instead of sinking behaviour at higher indentation depth. Within the realm of MD simulations, the simulated hardness value reached up to 16 GPa for initial indentation cycle. A steep drop in the load-displacement curve was observed during elastic-plastic transition signifying substantial strain softening of the substrate. It was found that the densely clustered stacking faults undergoes a reverse transition during cyclic loading, contributing to the back propagation phase responsible for elastic recovery, despite subsequent strain hardening. The study provides important insights into the underlying mechanisms governing the cyclic mechanical behavior of HEAs to guide their improved micromanufacturing.