Local chemical ordering coordinated thermal stability of nanograined high-entropy alloys

Nanograined (NG) materials often suffer from low thermal stability owing to the high volume fraction of grain boundaries (GBs). Herein, we investigate the possibility of utilizing local chemical ordering (LCO) for improving the thermal stability of NG FeCoNiCrMn high-entropy alloys (HEAs). NG HEAs with two different grain sizes were considered. Tensile tests and creep test simulations were then performed to reveal the influence of LCO on the mechanical properties and thermal stability of NG HEAs. After performing hybrid molecular dynamics and Monte Carlo simulations, Cr atoms were found to accumulate at GBs. By analyzing the atomic structure evolution during the deformation process, we found that the formation of LCO effectively stabilized the GBs and inhibited GB movement. In addition, dislocation nucleation from GBs and dislocation movement was also hindered. The inhibiting effect of LCO on GB movement and dislocation activity is more prominent than in the NG model with smaller grain sizes. The current simulation results suggest a possible strategy for enhancing the thermal stability of NG HEAs for service in a high-temperature environment.