Secondary phases characterization by SANS and XAS of an ODS ferritic steel after thermal aging at 873K

Abstract

An ODS steel with nominal composition Fe-14Cr-2W-0.4Ti-0.3Y2O3 (wt.%) was produced by mechanical alloying and compacted by hot isostatic pressing (HIP) followed by hot cross rolling (HCR). To check the effects of thermal aging at relevant temperatures of operation in fusion power plants, the alloy was thermally aged at 873 K for 2000 h. In this work, small-angle neutron scattering (SANS) and X-ray absorption spectroscopy (XAS) techniques are used for the advanced characterization of secondary phases and the oxide nanoparticle dispersion. SANS results show that the oxide nanoparticles remain stable after the thermal aging treatment. Composition of the oxide nanoparticles was identified as Y2TiO5 or Y2Ti2O7 by SANS, while non-stoichiometry was found by XAS analysis. Laves phase precipitation after the thermal aging treatment is further confirmed by SANS, from the magnetic anisotropic contribution to the scattering intensity associated to this metallic phase, and by XANES.