Characterisation of irradiation damage in Fe–3Cr and Fe–5Cr: A study on the effects of chromium content and temperature

Fe–Cr binary alloys serve as simplified model systems to study irradiation damage relevant to fusion structural materials. Here, Fe-3 %Cr and Fe-5 %Cr samples were irradiated with 4 MeV Fe ions under a dose rate of 4 × 10 −5 dpa/s across a linear thermal gradient (120°C-480 °C) in a single experiment, enabling direct comparison of temperature and Cr content effects under identical conditions. Depth-resolved Laue micro-diffraction (∼10 −4 strain sensitivity), nanoindentation, and AFM reveal non-monotonic evolution of lattice strain and hardness: both decrease with temperature up to ∼300 °C, then increase beyond. This turning point reflects changes defect mobility and solute-defect clustering, which stabilize damage. Fe-3 %Cr shows consistently higher strain and hardening than Fe-5 %Cr, especially at lower temperatures. Minimal change in post-indentation pile-up indicates limited softening or localization. These results highlight how Cr content and temperature jointly affect irradiation response, offering new insights into defect evolution in fusion-relevant alloys. • Single-sample irradiation under thermal gradient reduces variability in results. • Swelling decreases to 300 °C, then rises, marking a defect stability transition. • Higher Cr reduces swelling below 300 °C but shows no effect at higher temperatures. • Hardness vs temperature shows a V-shape with a minimum at 300 °C. • Strain penetrates ∼3 × deeper than SRIM prediction, implying high defect mobility.