Dispersoid coarsening induced softening in Ti-doped ODS-Cu alloys under Fe ion irradiation at 350°C

• Two ODS-Cu alloys show softening and dispersoid coarsening after irradiation at 350 ℃. • The mechanism of irradiation softening and dispersoid coarsening was revealed. • Larger initial-sized dispersoids are less prone to coarsening (Ostwald ripening). Oxide dispersion strengthened copper (ODS-Cu) alloy is considered as a candidate of heat sink materials for divertors, and Ti doping is regarded as an effective strategy to improve the performance of Cu-Al 2 O 3 (a common ODS-Cu). In order to evaluate the stability of the oxide nano-particles dispersed in Ti-doped ODS-Cu, irradiation was conducted using multiple-energy Fe ions at 350°C on two types of Ti-doped ODS-Cu with identical composition and oxide volumetric fraction while different size of oxide nano-particles. Ultimately, a 24 μm-thick quasi-homogeneous damaged layer of ∼ 1.35 dpa was induced in the specimens. Nano-hardness measurements were used to assess variation in the mechanical properties of the irradiated ODS-Cu. The results showed that both specimens experienced irradiation-induced softening, and softening in the specimen containing smaller sized particles is more pronounced. Microscopic observations reveal that the size of irradiated oxide nano-particles somewhat increased, which can be mainly explained by Ostwald ripening under irradiation, and this ripening effect is more pronounced in the smaller oxide nano-particles.