Improved irradiation resistance of accident-tolerant high-strength FeCrAl alloys with heterogeneous structures

Post–neutron irradiation examination is performed on advanced accident-tolerant fuel (ATF) cladding iron-chromium-aluminum (FeCrAl) alloys with ∼10–13at. % Cr, ∼10–12 at. % Al, ∼1 at. % Mo, and minor alloying elements including Y irradiated to a damage level of 7 displacements per atom (dpa) at irradiation temperatures of 267–282 °C. A compositional dependency of the Cr and Al content is observed on the ratio of sessile and glissile dislocation loops, where the density of a ⟨100⟩ type loops is somewhat higher than the a /2⟨111⟩ type loops. The α ′ precipitate number density is inversely correlated to the starting Cr concentration of the alloys of interest. The irradiation to a higher dose of 7 dpa results in a higher density of dislocation loops and α ′ precipitates for the same alloys at a lower irradiation dose, such as 1.8 dpa. In this work, the effect of α ′ precipitates on the dislocation loop density is discussed, and the presence of α ′ appears to inhibit the nucleation of loops. Compared with first-generation FeCrAl alloys, these advanced alloys with heterogeneous structure exhibit a lower Cr concentration in α ′ precipitation at the same dose level; they act as weaker obstacles deviating from the primary hardening contribution from the mature α ′. Hence, the overall irradiation-induced hardening decreases; our alloys show improved radiation resistance because of their stronger sink strengths. The results presented in this paper could provide insights for the design and optimization of ATF cladding materials for future fission and space applications.