Effect of interaction between bubbles and interfaces on irradiation hardening of vanadium alloy and ODS steel

Abstract

Defects induced by irradiation in a fusion reactor interact with interfaces and then affect the irradiation hardening of structural materials. The interaction between bubbles and interfaces was investigated using He⁺ irradiation at 500 °C for two candidate materials, V–4Cr–4Ti and 9Cr-ODS. The microstructure was observed, and nanoindentation testing was conducted to evaluate irradiation hardening. Microstructural analysis revealed that bubbles were produced in both samples, and precipitates were also found. The size of the intragranular bubbles in 9Cr-ODS were smaller than those in V–4Cr–4Ti. In 9Cr-ODS, the incoherent interface between Y₂TiO₅ particles and the matrix effectively hindered He diffusion, resulting in relatively smaller bubbles in the matrix. Significant bubble accumulation was observed at grain boundaries (GBs) in V–4Cr–4Ti, while in 9Cr-ODS, bubbles tended to gather at the interfaces between Y₂TiO₅ oxide particles and the matrix. Nanoindentation testing revealed that after He ⁺ irradiation, the hardness of V–4Cr–4Ti and 9Cr-ODS increased by 2.68 GPa and 1.89 GPa, respectively. This indicates that 9Cr-ODS has excellent irradiation hardening resistance ability, mainly because the interfaces between Y₂TiO₅ oxide particles and the matrix effectively captured bubbles, thus inhibiting their accumulation at GBs.