Microstructural analysis and mechanical implications of neutron-irradiated ITER-grade tungsten

This study examines the microstructural and hardening response of two ITER-grade pure tungsten materials, which were exposed to neutron irradiation at 600 °C and 1000 °C up to a dose of ∼1 dpa. Two major types of defects, dislocation loops and nanovoids, are observed for both grades and analyzed with transmission electron microscopy. While the general morphology and subgrain structure remained stable under irradiation, the number density of defects decreased, and average defect size increased at the higher irradiation temperature. Nanovoids exhibited greater thermal stability than dislocation loops, which led to their predominance in the radiation-induced hardening, particularly at 1000 °C. Hardening contributions were assessed using the dispersed barrier model, which showed that voids contributed more significantly to hardening than loops at any irradiation temperature. Various superposition rules are applied for the total hardening effect and the best fit is provided by squared summation with the size-dependent coefficient of barrier strength. The findings highlight the importance of void control and defect sink engineering in optimizing tungsten for fusion applications. This research aims to provide insights for designing radiation-resistant tungsten microstructure for advanced fusion reactor applications by linking defect behavior with mechanical properties under neutron irradiation.