Mechanical and microstructural behaviour of Y2O3 ODS EUROFER 97

Two small ingots of the steel EUROFER 97, one containing 0.25 wt% Y2O3 and the other Y2O3 free, have been produced by consolidating mechanically milled powder by hot isostatic pressing at 1373 K for 2 h under 200 MPa. For comparison, a third ingot was consolidated under identical conditions but using un-milled EUROFER powder. Microhardness, tensile and Charpy tests, along with TEM observations, have been performed on these materials in the as-HIPed condition and after different heat treatments. The mechanical behaviour and the microstructural characteristics of these materials suggest that the origin of the reduced impact properties of the oxide dispersion strengthened EUROFER could be the premature formation of carbides during quenching following the HIP process. This would be enhanced by the high density of structural defects produced by milling, as these favour the fast diffusion and segregation of carbon.