Effect of mechanical alloying atmosphere on the microstructure and Charpy impact properties of an ODS ferritic steel

Two types of oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe–14Cr–2W–0.3Ti–0.3Y2O3 (in weight percent), have been produced by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y2O3 particles either in argon atmosphere or in hydrogen atmosphere, degassing at various temperatures, and compacting the mechanically alloyed powders by hot isostatic pressing. It was found in particular that mechanical alloying in hydrogen yields a significant reduction in oxygen content in the materials, a lower dislocation density, and a strong improvement in the fast fracture properties of the ODS ferritic steels, as measured by Charpy impact tests.