Evaluation of hardening behaviors in ion-irradiated Fe–9Cr and Fe–20Cr alloys by nanoindentation technique

The ion irradiation hardening behaviors of Fe–9 wt% Cr and Fe–20 wt% Cr model alloys were investigated by nanoindentation technique. The specimens were irradiated with 3 MeV Fe11+ ions at room temperature up to 1 and 5 dpa for Fe–9Cr alloy and 1 and 2.5 for Fe–20Cr alloy. The ratio of average hardness in the same depth of irradiated and unirradiated (Hirr. av/Hunirr. av) was used to determine the critical indentation depth hcrit to eliminate the softer substrate effect. The Nix–Gao model was used to explain the indentation size effect. Irradiation hardening is clearly observed in both Fe–9Cr alloy and Fe–20Cr alloy after ion irradiation. The differences of ISE and irradiation hardening behaviors between Fe–9Cr and Fe–20Cr alloys are considered to be due to their different microstructures and microstructural evolution under ion irradiation.