Suppressing effect of tantalum on the radiation-induced clustering of rhenium in tungsten

Using the first-principles calculations and object kinetic Monte Carlo (OKMC) methods, we systematically investigate the influence of tantalum (Ta) on the behaviors of rhenium (Re) in tungsten (W) without and with irradiation defects, i.e., vacancies and self-interstitial atoms (SIAs). Due to the attractive interaction of Ta-Re pair, the Ta atoms energetically prefer to occupy the sites inside the pure Re clusters and Re-vacancy complexes. Conversely, there are strong repulsive interactions between Ta and large Re-SIA complexes in W. Therefore, the Re-rich clusters in irradiated W-Re-Ta alloys are largely composed of Re-SIA complexes, because of the experimental observation that the Ta atoms are ejected by the clusters. More importantly, the Ta addition reduces not only the mobility of SIA and interstitial Re but also the stability of interstitial-type Re clusters, and thus hinders the formation of Re-rich clusters in W both kinetically and thermodynamically. This is confirmed by the OKMC simulations, in which the presence of Ta significantly decreases the average size, total volume and density of Re-rich clusters in irradiated W. These results are in good agreement with the experiments. Consequently, the present study will deepen the mechanistic understanding of the role of Ta on the aggregation of Re atoms in W after irradiation and provide a valuable reference for the development of advanced W-based materials.