The effect of W2+ irradiation and He+ exposure on W-Ta alloy fabricated via SPS.

• W alloy irradiated by W2+ and He+. • Pre-damage accelerates the growth of the fuzzy structure to the shedding stage. • Ta-enriched grains show fragmentation under He+ irradiation. Tungsten (W) has been selected as the material for the divertor in ITER due to its good thermal and mechanical properties, and alloying of tungsten has been considered as a potential way to enhance the properties of tungsten. However, the effect of the alloying elements on the irradiation resistance of the material still need to be studied. In this study, we prepared tungsten-tantalum (Ta) alloys, namely, W-1wt%Ta and W-3wt%Ta, by spark plasma sintering (SPS). The feedstock powder was obtained by ball-milling and mixing of W and Ta powders. The bulk material containing a large number of W grains with Ta at the grain boundaries (Ta-enriched grains) was obtained by rapid sintering via SPS. The alloy was subsequently irradiated with high-energy W self-ion (W2+) irradiation and low-energy and high-flux helium ion (He+) irradiation, for exploring the irradiation resistance of the alloy. Ta-enriched grains were found to be more susceptible to the damage by He+, the Ta-enriched grains located near the fuzz layer are damaged by He+. Pre-damaged sample (samples were first irradiated via W2+ ion before He+ irradiation) shows more sparse fuzzy structure than the non-pre-damaged samples. This work explores the effect of the presence of Ta-enriched grains on the irradiation resistance and provides reference information for the irradiation performance of other materials with the presence of enrichment element at the grain boundaries. [ABSTRACT FROM AUTHOR]