Role of Nano-Oxides in Suppressing Dislocation Loop: A Comparison of 12Cr-ODS Steels and Non-ODS Model Alloy

To clarify how Y-Ti-O nano-oxides mitigate radiation damage, this study presents a depth-resolved comparison between fully recrystallized 12Cr oxide-dispersion-strengthened (ODS) steels and an Fe-12Cr model alloy. By normalizing the microstructures through heat treatment before irradiation, the intrinsic influence of nano-oxides was isolated from other defect sinks. Both materials were irradiated with Fe2+ ions to 2 dpa at 400°C, enabling direct evaluation of defect evolution under identical conditions. Transmission electron microscopy (TEM) revealed that the ODS steels developed substantially lower dislocation-loop densities and smaller, more uniform loop sizes than the Fe-12Cr alloy. The ODS steels also exhibited a dominant population of 1/2〈111〉 interstitial loops, whereas the model alloy formed both 〈100〉 and 1/2〈111〉 loops with large depth-dependent fluctuations. Nano-indentation testing further demonstrated that irradiation-induced hardening in the ODS steels was significantly reduced, consistent with dispersed barrier hardening calculations based on the observed microstructure. These results provide direct experimental evidence that nano-oxides destabilize defect evolution, suppress loop growth, and mitigate hardening, offering mechanistic insight for the design of advanced radiation-tolerant materials.