| Summary: | A study of high-temperature defect recovery has been carried out for W-5 wt% Ta alloy, irradiated with 2 MeV W+ ions at 500 °C, up to 1.2 dpa. After post-irradiation annealing at 1200 °C for 15 min, the damage microstructure evolved from a random distribution of small loops to a mixture of large loops, dislocation lines and voids. The average size of loops increased by a factor of ∼4, up to 17.7 nm, whereas the number density dropped by an order of magnitude, to ∼5.3 × 1021 m−3. Only loops with b = ½<111> were observed and they were identified to be exclusively interstitial type. This is in sharp contrast with the presence of ∼25% vacancy type ½<111> loops in the as-irradiated condition. Voids were formed as a result of accelerated vacancy/vacancy-cluster migration at 1200 °C, achieving an average size of ∼2.5 nm and a high density of ∼5.1 × 1022 m−3. The role of tantalum is discussed. Furthermore, the high-temperature defect recovery in W-5Ta after self-ion (this work) and proton irradiations (Ipatova et al., 2017) are compared, based on which the possible influence of hydrogen upon defect evolution is discussed. Keywords: High-temperature, Defect recovery, Self-ion irradiation, W-5Ta
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