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

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 M23C6 particles. Static recovery was found to be the predominant softening mechanism of this steel in the investigated temperature range.