Characterization of the defects in oxide dispersion-strengthened iron alloy after helium ion irradiation

Vacancy-type defects in Fe-2%Al₂O₃ (ODS-Fe) and pure Fe produced by helium ion irradiation at room temperature were investigated using positron beam Doppler broadening energy spectra (DBES). Defect profiles of the S parameter derived from DBES as a function of positron incident energy up to 20 KeV were analyzed. The S parameter values of the damaged layer for the ODS-Fe are smaller than those of pure Fe for irradiation dose of 1e+16/cm². This finding indicates that ODS-Fe has a higher irradiation resistance than pure Fe. It also suggests that helium irradiation induced point defects in ODS-Fe were trapped and annihilated at the interfaces between the Fe matrix and the Al₂O₃ nanoparticles. The S-W curves indicate that only one type of defect was formed in the post-irradiated ODS-Fe. Vacancy clusters and helium-vacancy complexes were identified as the main defects. The defects are complicated for the irradiated pure Fe, for which the surface defects are different from the ones inside bulk.