Nanomechanical testing of ODS steels irradiated with 1 MeV/amu heavy ions

Heavy ion beams with high damage production rate are widely used to evaluate radiation tolerance of promising nuclear reactor materials, such as oxide dispersion strengthened (ODS) alloys, including their mechanical properties. Since typical ion projected ranges do not exceed 1 micron, nanoindentation technique is the most convenient method for examination of irradiated materials. In present work we report data on radiation hardening of several ODS steels irradiated with 107 MeV Kr and 167 MeV Xe ions. Some samples were irradiated trough the special Al-foil filter in order to obtain the unfolding damage profile on the surface. The post-irradiation testing steels included conventional nanoindentation measurements and CSM for determination of possible size effects associated with indentation size effect as well as soft surface effect. Swift heavy ion induced changes in microstructure evolution were studied by transmission electron microscopy (TEM). It was found that hardening of the ODS steels irradiated with krypton and xenon ions of fission fragment energy for damage dose about 1 dpa level is in the range 5-25% (figure 1). TEM examination have revealed complete amorphization of carbide and (Y,Ti) oxide particles in ferritic matrices as a result of multiple amorphous latent track overlapping. At the same time no dissolution of nano-oxide particles was observed. This implies that radiation hardening is not due to changes in morphology of nanoparticles