Investigate irradiation hardening behavior in BCC refractory high-entropy alloys using phase-field modeling informed by atomistic simulations of displacement cascades

Refractory high-entropy alloys (RHEAs) exhibit excellent anti-irradiation properties, making them promising candidates for application in advanced nuclear reactors. In this study, molecular statics (MS) and molecular dynamics (MD) simulations are conducted to investigate the local unstable stacking fault energy (USFE) in RHEAs induced by primary knock-on atoms (PKAs) of displacement cascades. Based on these atomistic simulations, a phase-field dislocation dynamics (PFDD) model is developed, incorporating the effects of chemical composition fluctuations and displacement cascades on local USFE in RHEAs using a random statistical approach. Using this PFDD model, the planar motion of edge and screw dislocations, as well as the cross-slip behavior of screw dislocations, in WTaCrV are examined. The results indicate that the cascade region can effectively pin edge dislocations and hinder the nucleation of kink pairs in screw dislocations, leading to irradiation hardening. However, the low local USFE caused by chemical composition fluctuations in WTaCrV allows edge dislocation segments near pinning sites to bow out, dragging pinned dislocation segments and reducing the pinning effect. Additionally, the low local USFE promotes the nucleation and migration of kink pairs in screw dislocations. Furthermore, for the case of screw dislocation cross-slip, the irradiation hardening is alleviated as nonplanar kink pairs recede to the habit plane. These simulation results reveal the mesoscale internal mechanisms underlying anti-irradiation hardening in RHEAs. Based on these findings, mesoscale theoretical models describing dislocation motion and irradiation hardening are proposed, and they are verified experimentally. With these models, the irradiation hardening behavior of other RHEAs can be predicted. These findings can guide the design and preparation of advanced anti-irradiation RHEAs and contribute to the development of upscaled theoretical models and simulation methods.