Microstructural development and irradiation hardening of W and W–(3–26) wt%Re alloys after high-temperature neutron irradiation to 0.15 dpa

Microstructural development and irradiation hardening for irradiated W and W–3, 5, 10, 26 wt % Re alloys have been investigated using transmission electron microscopy and hardness measurement. Neutron irradiation is performed to 0.15 dpa at 873, 1073, 1273 K and at variable temperatures 873/1073 K in the Japan Materials Testing Reactor. Neutron radiation-induced voids, dislocations and dislocation loops that result in irradiation hardening are observed and evaluated for microstructural development. The combination of W with Re effectively prevents irradiation damage since the number density and radius of both voids and dislocation loops remarkably decrease with increasing Re content. The process of void growth in irradiated W depends on temperature during irradiation and occurs at T/Tm ≈ 0.3 (T: temperature during irradiation; Tm: melting point of W). The varying temperature irradiation tends to enhance the recombination between vacancies and interstitials, which significantly reduces the density of dislocation loops. The results of observation reveal that grain boundaries can restrain the growth of dislocations and dislocation loops.