Development of an oxide dispersion strengthened, reduced-activation steel for fusion energy

A reduced-activation steel having a nominal chemical composition of Fe, 9% Cr, 2% W, 0.25% V, 0.1% Ta, and 0.1% C was mechanically alloyed with a fine dispersion of Y2O3 and TiO2 to assess the potential for extending the elevated temperature limit of this alloy for structural applications. The total oxide dispersion content was varied from 0.25% to 1% and the molar ratio, TiO2/Y2O3 from 0 to 2. An argon atomized 9Cr2WVTa steel powder was ball milled under vacuum, extruded at 1150°C to a 16 to 1 reduction in area, followed by a normalize and age heat treatment. Mechanical properties were assessed by elevated temperature tensile tests over the temperature range from room temperature to 800°C. Transmission electron microscopy revealed a favorable dispersion of the oxide particles. Oxide dispersion strengthening by mechanical alloying resulted in significant improvement in elevated temperature tensile strengths. Extended ball-milling times improved oxide dispersion, microstructural refinement, and mechanical properties.