Achieving excellent mechanical properties of ODS steel by Y2O3 addition

Abstract

As a candidate material for fuel cladding in fission reactors, the mechanical properties of ODS-Ferritic/martensitic (F/M) steel should be further improved. Incorporating oxide nanodispersions with a high number density into the matrix is a promising strategy. In this study, the incorporation of the ultra-high number density of Y2O3 oxide nanoparticles in ODS steel was achieved by adding Y2O3 during Hot Isostatic Pressing (HIP), and the microstructure and properties were optimized by performing hot rolling deformation. The addition of Y2O3 has revealed two effects: the non-loss part of Y2O3 powder forms part of Y2O3 particles during HIP; the loss part generates a certain concentration of oxygen in the tank and reacts with yttrium element to generate another part of Y2O3 particles. Following HIP, a bimodal ferrite structure and reticular M23C6 carbides distributed along grain boundaries are revealed. The grain size and M23C6 carbide are remarkably refined following hot rolling while the Y2O3 particle size did not increase significantly. Due to dispersion and fine grain strengthening, and the effect of elimination of reticular M23C6, an excellent combination of strength (1474 MPa) and ductility (13%) has been achieved in ODS steel prepared by the HIP with Y2O3 addition and hot rolling.