Optimization of the thermomechanical treatment to achieve a homogeneous microstructure in a 14cr ODS steel

International audienceOxide dispersion strengthened (ODS) ferritic steels are promising candidates for high burn up fuel pins of Sodium Fast Reactors and structural materials in fusion reactors. They are elaborated by powder metallurgy and their manufacturing route is complex and specific, including hot forming and cold working. Different heat treatments are necessary to recrystallize these materials and to relieve internal stresses. The presence of highly stable nano-oxydes and the limited stored energy after elaboration can make the recrystallization temperature extremely high (> 0.9 Tmelting). In this paper, a model alloy was studied before and after specific deformation by cold working. It appears that after being hot-extruded, the material cannot be recrystallized due to the very high stability of the nano-particles. Otherwise, cold deformation after extrusion is necessary to trigger recrystallization. In that case, the microstructure obtained after annealing is weakly textured and the size of the nano-particles is not affected