Annealing Behavior of Ferritic-Martensitic ODS-Eurofer Steel: Effect of Y_2O_3 Particles On Recrystallization

摘要

Reduced activation ferritic-martensitic steels are considered for future applications in fusion power plants. The thermal stability of two steels (ODS-Eurofer and Eurofer-97) was evaluated in cold-rolled samples annealed below 800℃. These grades have similar chemical compositions except for the presence of nanosized Y_2O_3 particles in ODS-Eurofer steel. This nanosized dispersion is very effective to prevent recrystallization. On the other hand, full recrystallization occurs in Eurofer-97 steel when annealed above 700℃. The low volume fraction of recrystallized grains (< 0.1) in ODS-Eurofer steel annealed at 800℃ can be explained by nucleation at prior grain boundaries and around large M_(23)C_6 particles. Further growth of these nuclei is impeded by Zener drag and concurrent recovery. Static recovery is the main softening mechanism in the ODS-steel below 800℃.