[3N01-07] Structural Materials for Blankets

[3N03] Effect of titanium concentration on nitrogen migration in low-activation vanadium alloys

*Kazuki Saito¹, Makoto I. Kobayashi^1,2, Jingjie Shen^1,2, Gaku Yamazaki¹, Takuya Nagasaka^1,2, Valentyn Tsisar³, Takeo Muroga^1,2 (1. SOKENDAI, 2. NIFS, 3. SCK•CEN)

Keywords:fusion reactor structural material, vanadium alloy, nitrogen, scavenging effect, mechanical properties

Low-activation vanadium alloys (V-4Cr-4Ti) are candidate structural materials for liquid lithium breeding blankets. The embrittlement of V-alloys, which occurs by solid solution hardening due to impurity nitrogen transported from lithium, is of concern. Alloying element titanium forms precipitates with nitrogen and suppresses the embrittlement, but its concentration should be minimized to reduce radioactivity. This study, simulating the nitrogen transportation by nitrogen exposure, quantitatively evaluated the correlation among nitrogen diffusion, precipitation behaviors, and mechanical properties of the alloys. As the titanium concentration increased, the hardening area due to nitrogen dissolution decreased. The hardening range could be calculated based on the one-dimensional diffusion model with the trapping reaction for the diffusant nitrogen by titanium. Calculation results including precipitation hardening are also reported.