Martensite transformation induced superplasticity and strengthening in single crystalline CoNiCrFeMn high entropy alloy nanowires: A molecular dynamics study

In this work, we report simultaneous superplasticity and strengthening in single crystalline face-centered cubic (FCC) CoNiCrFeMn high entropy alloy (HEA) nanowires through synergistic martensitic phase transformation and micro-twin nucleation as revealed by molecular dynamics simulations. Furthermore, in contrast to the irreversible martensite transformation that has been previously reported in bulk HEAs under high pressure, the martensitic transformation in HEA nanowires is found to be reversible upon reverse loading. Shape memory effects can thus be enabled in HEA nanowires, although such effects are found to be mitigated for some orientations due to stacking fault crossing. Those mechanisms are dramatically different from deformation twinning dominated superplasticity in conventional FCC metal and intermetallic nanowires. While deformation twinning is still observed in FCC HEA nanowires, three pathways are found and in particular. All the novel mechanical behaviors in FCC CoNiCrFeMn HEA nanowires reported in this study can be explained by their unique negative stacking fault and martensite energies, which may shed some light on understanding the mechanical behavior of general HEAs under more complicated loading conditions.