Annealing behavior of ferritic–martensitic 9%Cr–ODS–Eurofer steel

Abstract

Oxide dispersion strengthened ferritic–martensitic steels are potential candidates for applications in future fusion power plants. High creep resistance, good oxidation resistance, reduced neutron activation and microstructural long-term stability at temperatures of about 650–700 °C are required in this context. In order to evaluate its thermal stability in the ferritic phase field, samples of the reduced activation ferritic–martensitic 9%Cr–ODS–Eurofer steel were cold rolled to 50% and 80% reductions and further annealed in vacuum from 300 to 800 °C for 1 h. The characterization in the annealed state was performed by scanning electron microscopy in the backscattered electron mode, high-resolution electron backscatter diffraction and transmission electron microscopy. Results show that the fine dispersion of Y-based particles (about 10 nm in size) is effective to prevent recrystallization. The low recrystallized volume fraction (<0.1) is associated to the nuclei found at prior grain boundaries and around large M 23C 6 particles. Static recovery was found to be the predominant softening mechanism of this steel in the investigated temperature range.