The effect of initial microstructure on the irradiation hardening of the W fiber in Wf/W–Y2O3 composites

Tungsten fiber-reinforced tungsten (W f /W) composites are promising candidates for plasma facing materials for fusion devices. The hardening behaviors of unrecrystallized W fiber (NRX-W fiber) and fully recrystallized W fiber (RX-W fiber) in the W f /W-Y 2 O 3 composites after helium ion irradiation (180 keV) were studied. The results reveal that the lattice distortion and microscopic residual stress in both the NRX-W fiber and the RX-W fiber increase after irradiation. The observation of dislocation loops with lower number density and smaller size in the NRX-W fiber compared to the RX-W fiber indicates that the NRX-W fiber has an enhanced capacity for capturing irradiation-induced defects. This enhanced capacity arises from its characteristics, including an initially larger proportion of high-angle grain boundaries (HAGBs), a higher density of subgrain boundaries, and geometrically necessary dislocations (GNDs). Nanoindentation tests show that the irradiation hardening increments for NRX-W fiber and RX-W fiber are 4.38 ± 0.10 GPa and 5.08 ± 0.17 GPa, respectively. Notably, the irradiation hardening rate of NRX-W fiber is 52.96%, which is significantly lower than that of RX-W fiber (84.95%), indicating superior resistance to helium ion irradiation hardening in the NRX-W fiber. Consistent with these experimental findings, theoretical calculations using the dispersed barrier hardening (DBH) model yield irradiation hardening increments of 3.68 GPa and 4.99 GPa for NRX-W fiber and RX-W fiber, respectively. Additionally, dislocation loops exhibit a uniform distribution within the equivalent crystallographic direction, with their contributions being dominant in the irradiation hardening of both fiber types.