Molecular dynamics study on displacement cascade simulation and void strengthening effect in Fe-Ni-Cr alloy

Abstract 800H alloy (Fe-Ni-Cr-based alloy) is considered to be a key candidate structural material for advanced reactors in the future. During the service process, irradiation-induced defects are a key factor affecting the performance of alloys and can lead to irradiation hardening. This study first investigated the evolution of defects in the Fe 46 Ni 32 Cr 22 alloy during the primary displacement cascade process under different PKA energy ( E PKA ), as well as the effect of irradiation on its mechanical properties. Based on the phenomenon of increased flow stress in the irradiated alloy, a dislocation-void interaction model was established, and the void strengthening effect was analyzed at different temperatures and void sizes. The results show that vacancies tend to form small-sized clusters (1–10 Å), while interstitial atoms are more likely to aggregate into large-sized clusters (50+ Å). E PKA exerts a significant influence on the evolution of defects, as E PKA increases, the defects first evolve from clusters into interstitial dislocation loops and stacking fault tetrahedral, and finally exist in the form of mixed dislocation loops. Irradiation reduces the yield strength of the alloy and induces the early onset of yielding. The increase in flow stress is mainly attributed to the strengthening effect of voids on the critical resolved shear stress, and the strengthening effect increases with the increase in void size and decreases with the rise in temperature.