Effects of Mo/Zr addition on deuterium retention in W-Y2O3 alloys

Abstract Mo/Zr were added to further improve the mechanical properties of W-Y2O3 alloys, thus improving W ductility due to the addition of Y2O3 nanoparticles. Herein, the effects of minor addition of elemental Mo/Zr and Fe-ion pre-irradiation on D retention in W-Y2O3 alloys were investigated. The maximal fluence of W-1 wt.%Mo-0.25 wt.%Y2O3 and W-0.1 wt.%Zr-0.25 wt.%Y2O3 samples irradiated with 5-keV-energy D2 ions was 1022 D2/m2, and Fe-ion pre-irradiation was performed at ion fluences of up to 4 × 1018 /m2 at the energy of 1 MeV. For both alloys, the D desorption amount increased with increasing D2-ion irradiation fluence, regardless of Fe-ion pre-irradiation. Compared with W-Y2O3, the overall amount of the D desorption increased for both alloys without Fe-ion pre-irradiation. However, it decreased for both alloys with Fe-ion pre-irradiation, when the D2-ion irradiation fluence was 1022 D2/m2. The addition of Mo/Zr prevented the diffusion of D from the surface to the inside of the sample. Therefore, Fe-ion pre-irradiation had a negligible effect on D desorption in the Mo- or Zr-added W-Y2O3 alloys. Changes in the microstructures of the W alloy owing to the addition of minor elements strongly affected the D desorption. The addition of Mo promoted the formation of dislocation loops during the D2-ion irradiation. In contrast, the addition of Zr refined the Y2O3 particles. These defects served as D trapping sites, thereby weakening the pre-irradiation effect of Fe ions.