Annealing Behavior of RAFM ODS-Eurofer Steel

Oxide-dispersion-strengthened (ODS) ferritic-martensitic steels are candidates for applications in fusion power plants where microstructural long-term stability at temperatures of [approximately]650°C to 700°C are required. The microstructural stability of 80% cold-rolled reduced-activation ferritic-martensitic 9% Cr ODS-Eurofer steel was investigated within a wide range of temperatures (300°C to 1350°C). Fine oxide dispersion is very effective to prevent recrystallization in the ferritic phase field. The low recrystallized volume fraction (<0.1) found in samples annealed at 800°C is associated with the nuclei found at prior grain boundaries and around coarse M₂₃C₆ particles. The combination of retarding effects such as Zener drag and concurrent recovery decrease the local stored energy and impede further growth of the recrystallization nuclei. Above 900°C, martensitic transformation takes place with consequent coarsening. Significant changes in crystallographic texture are also reported.