Atomistic simulation of the interactions of radiation damage and grain boundaries in austenitic FeCrNi alloy

Austenitic FeCrNi (Fe-20Cr-10Ni) alloy is considered one of the potential structural materials for fourth generation nuclear reactors due to its excellent mechanical properties, corrosion resistance, and radiation resistance. In its study of radiation damage, grain boundary (GB) design is one of the effective strategies to improve its radiation resistance, as GBs can significantly reduce radiation damage by absorbing radiation-induced defects. However, the understanding of the relationship between GB characteristics and radiation resistance is still unclear. This study investigated the cascade collision process of six FeCrNi bi-crystals with different GBs through atomistic simulation, aiming to investigate the defect absorption characteristics of different types of GBs in FeCrNi alloy. The results indicate that compared to the single crystal, the presence of GBs in the bi-crystals can effectively help absorb radiation-induced point defects, thereby suppressing the formation of a large number of clusters and the evolution of dislocation loops and stacking fault tetrahedra. The defect absorption efficiency is determined by the excess energy of GBs, and a universal logarithmic relationship exists between these two parameters. After radiation, there is a clear "U-shaped" relationship between the reduced yield strain/stress and the excess energy of GB. In addition, the rearrangement of displaced atoms in GB induced by radiation leads to GB migration and the formation of new GB facets on the {111} plane. Besides, the interaction between radiation-induced point defects and GBs leads to Ni segregation and Cr depletion in the GBs. This study not only contributes to a deeper understanding of the interaction between radiation-induced defects and GBs, but also provides guidance for breaking through the radiation resistance limit of FeCrNi alloys through anti-radiation GB engineering.