Nanosized oxide phases in oxide-dispersion-strengthened steel PM2000

Oxide-dispersion-strengthened (ODS) steels are promising material candidates for nuclear fission and fusion applications. Nanosized oxide particles in as-rolled ODS steel PM2000 were investigated by using transmission electron microscopy. Uniformly distributed nanosized particles and heterogeneously distributed large dispersoids were observed in the steel. Three nanosized oxide phase types, Al2Y4O9, Y3Al5O12 and YAlO3, were present in the steel. Nanosized aluminum yttrium oxide Al2Y4O9, which has an orthorhombic P Bravais lattice rather than a monoclinic P Bravais lattice, was identified. Nanosized yttrium aluminum oxides that consisted of Y3Al5O12 and YAlO3 were also identified. The formation mechanism of Al2Y4O9/Y3Al5O12/YAlO3 phases in the steel resulted from the processing (hot-extrusion/hot-rolling) procedures. Al diffusion from the steel matrix into the Y2O3 particle fragments induced the nucleation and growth of the Al2Y4O9/Y3Al5O12/YAlO3 phases.