Nanoindentation of model Fe–Cr alloys with self-ion irradiation

Pure Fe and Fe–Cr alloys containing 3%Cr, 5%Cr, 7%Cr, 9%Cr and 12%Cr were subjected to Fe+ implantation to a low dose (2.06 dpa) and high dose (6.18 dpa) with energies of 2 MeV and 0.5 MeV and at a temperature of 320 °C. This created a damage layer of approximately 800 nm depth at the sample surface. Nanoindentation tests were performed in un-irradiated and irradiated regions of the same grain for each sample, to avoid complications arising from crystal anisotropy. Cross-sections of indents with depths ranging from 50 to 250 nm in un-irradiated and irradiated regions of the same grain in the high dose Fe12%Cr sample were analysed in the TEM. The main plastic zone was contained within the damage layer for indentation depths up to 200 nm. Irradiation hardening saturated at the lower dose in high Cr content samples, but alloys with lower Cr content exhibited further hardening when subjected to the higher dose. Dislocation channelling was observed in the high dose Fe12%Cr sample, suggesting that defects were absorbed by glissile dislocations.