In order to improve the fundamental understanding on the microstructural behavior of irradiated Fe-Cr alloys, model alloys of high-Cr ferritic-martensitic (F-M) steels candidates as structural materials for Gen IV nuclear power plants, a nanoscale description of the microstructure has been performed as a function of Cr concentration and irradiation temperature. Two series of experiments have been undertaken: ● Fe-5%Cr, Fe-9%Cr and Fe-12%Cr model alloys have been neutron irradiated up to 0.6 dpa at 300°C (the minimum operating temperature of ferritic-martensitic steels in Generation IV reactors). 3D atom probe (3DAP) study has shown that the impurities are also involved in the microstructural evolution under irradiation. Two independent populations of clusters inside the grains have been revealed. The first family, NiSiPCr-enriched clusters have been observed in all the model alloys. The second one, Cr-enriched clusters which correspond to α' clusters, have been observed in the Fe-9%Cr and Fe-12%Cr model alloys. This work has shown that the NiSiPCr-enriched clusters are radiation induced segregations whereas the appearance of Cr-enriched clusters originates from radiation enhanced process. Enrichment in Si, P and Cr has been revealed on dislocation lines, low-angle and high-angle grain boundaries in all model alloys. ● Ion irradiation of the Fe-9%Cr and Fe-12%Cr model alloys has been performed at 500°C (temperature close to the maximum operating temperatures of ferritic-martensitic steels in Generation IV reactors). In-situ TEM study has shown that during 150 keV Fe + ion irradiation at 500°C up to 1.5 dpa, damage becomes apparent in the form of randomly distributed dislocation loops. In both model alloys after 1.5 dpa the loops are mainly of [100]-type. 3DAP study of the same alloys irradiated under the same conditions but in the form of sharp tips did not reveal any chemical species redistribution. This work has been supported by the European Commission within the project GETMAT under grant agreement FP7-212175.
