An Fe8Cr model alloy was irradiated in the TIARA facility with 10.5 MeV Fe 3+ ions and/or 1.05 MeV He + ions at 100300°C to 0.1 10 dpa. Irradiated specimens were characterized using transmission electron microscopy and a nano-indentation technique. Visible defect clusters were not detectable by TEM for doses below ³0.1 dpa, while spatially heterogeneous dislocation loop rafts were visible for a dose of 10 dpa in single ion irradiation. The loop rafts formation was impeded in dual ion irradiation with the implantation of helium atoms at 10 dpa. Ion irradiation led to increases in hardening with increasing doses. Further, log-log plots of irradiation hardening at 100, 250 and 300°C, which fit the dose dependence of the irradiation hardening using ¦H £ (dpa) n , indicate that the decreases of n values with lower temperatures are due to a tendency towards saturation in the irradiation hardening.