Amorphization of oxides in ODS materials under low and high energy ion irradiations

Oxide Dispersion Strengthened (ODS) ferritic/martensitic (F/M) steels are promising materials as structural components for fusion reactors. Their excellent creep properties are provided by the nano-dispersed oxides reinforcing the material. This oxide dispersion has to be as stable as possible under irradiation at high temperatures.In the present work, low and high energy ion irradiation experiments were used to investigate microstructural stability under irradiation of oxides. Two iron base ODS alloys were studied: the ODS DY reinforced by yttrium and titanium oxides and the ODS EM10 reinforced by magnesium oxides. TEM investigations of the crystallinity for large oxides (d ≈ 50 nm) after irradiations reveal that, in both alloys, amorphization can occur due to electronic excitations or ballistic damages. Amorphization appears to depend on the nature of the oxides. Low energy ion irradiation results show that a critical temperature and a critical dose may exist, for which no amorphization is observed.