Rate theory and experimental study of the irradiation induced defects in molybdenum alloy

Highlights: • Molybdenum alloys were irradiated with self-ion Mo³⁺ up to 10 dpa. • No voids were observed due to the inhibition of voids growth in high dose rate and the low mobility at 330 ℃. • Ion irradiation experiments and rate theory simulation are combined to investigate the evolution of defects. • Rate theory were used to study the effect of dose rates and temperatures on microstructrues in molybdenum alloy. -- Abstract: Molybdenum alloys were irradiated with 3 MeV Mo³⁺ to 1–10 dpa (displacement per atom) at 330 °C. Transmission electron microscopy (TEM) observation and rate theory simulation were performed to investigate the evolution of defects induced by irradiation. A large number of fine dislocation loops were induced after irradiation, and dislocation network appeared above 5 dpa. Both experiment and simulation show that the growth rates of dislocation loops and voids decrease with the dose, which can be attributed that interstitial atoms and vacancies annihilate with the previously existing defect clusters. No voids were observed in all irradiated specimens due to the inhibition of voids growth in high dose rate and the low mobility at 330 °C. Furthermore, simulation shows that higher dose rate and low temperature result in higher saturated volume densities of loops and voids. Voids appear earlier and are larger at higher temperatures because of active diffusion of vacancy at higher temperatures. The swelling and hardening peak temperature in ion irradiation were higher than that in neutron irradiation, which might be a temperature compensate for higher dose rate of ion irradiation.