Nanoindentation of ion-irradiated Fe-Cr alloys

The structural materials of particular components in nuclear applications like fission or fusion reactors are exposed to high neutron fluxes giving rise to the formation of irradiation-induced defects and subsequent changes of the mechanical properties. Ion-irradiation is a well-recognized tool to simulate damage caused by fast neutron irradiation in a wide range of irradiation temperature and fluence and allows for an efficient screening of potential structural materials for nuclear application due to short irradiation times. The limited depth of penetration of the ions into the material (up to few µm) demands characterization methods suitable for thin layers. In the present work, nanoindentation is applied to deduce the irradiation-induced hardness changes. The approach is based on the generation of an approximately rectangular dpa-profile by means of multi-step irradiations with ions of different energies and the exploitation of the depth dependence of the hardness. Results will be reported for ferritic/martensitic Cr-steels considered as candidate structural materials for future application in Generation IV fission reactors and for Fe-Cr binary alloys with emphasis on the effect of irradiation temperature and fluence. Transmission electron microscopy results on the formation of irradiation-induced defects will be taken into account.