Abstract: Rhenium (Re) alloying is generally considered as an effective method to improve the performance of body-centered cubic (bcc) refractory metals, while the transmutation Re may adversely affect the thermo-mechanical property of bcc tungsten (W) under neutron irradiation. This highlights the importance of the Re introduction method in determining its effects on bcc metals, a factor that has yet to be fully clarified. In this study, we systematically investigate the co-evolution of Re and irradiation defects in W using the object kinetic Monte Carlo (OKMC) method, considering different Re introduction methods and transmutation rates. It is found that the extent of Re aggregation in neutron-irradiated pure W (with continuous Re introduction via nuclear transmutation) is significantly greater than in ion-irradiated W-Re alloys (where Re is introduced only at the initial stage in the solid solution state), even with identical Re concentrations. These differences align well with experimental observations and can be explained by the Re-to-defect ratio and the mobility of Re atoms, both of which strongly depend on the Re introduction method. Moreover, we quantify the volume fraction of irradiation defects and the average Re concentration in Re clusters within W-Re system across various transmutation rates, identifying critical conditions for Re’s transition from beneficial to detrimental. Our findings provide valuable insights for assessing Re effects in neutron and ion irradiated W-Re systems and support the application of bcc refractory metals in nuclear environments.

Key words: Alloying elements, Rhenium effect, Irradiation defects, Microstructural evolution