Effect of Cold Rolling on Recrystallization Behavior of Al-Free and Al-Added 15Cr-ODS Ferritic Steels

The effect of cold rolling on the recrystallization behavior of Al-free and Al-added 15Cr-oxide dispersion strengthened (ODS) ferritic steels was investigated. The recrystallization of both steels are enhanced by cold rolling. The Al-free ODS steel with finer oxide particles is harder to recrystallize than Al-added ODS steel with coarser oxide particles. The effect of Al addition on the recrystallization behavior is evident. It is estimated that the recrystallization temperature of Al-free and Al-added 15Cr-ODS ferritic steel is 900 degrees C and 1250 degrees C with the annealing period of 1 h. In Al-free ODS steel, a small hardening was observed in the temperature range between 850 degrees C and 1200 degrees C, while no such phenomenon was observed in Al-added ODS steel, which is indicative of retardation of recovery by finely dispersed oxide particles. Oxide particle growth is mostly dependent on annealing temperature, while recrystallization and grain growth are controlled by not only the temperature, but the cold rolling ratio, which alters the multiple factors such as dislocation density, initial grain shape and oxide particle dispersion morphology. The cold rolling direction also influences the grain morphology and grain orientation in Al-added ODS steel, and the second rolling in a perpendicular direction to the first cold rolling direction induces the rotation of the grains from to . The recrystallization temperature is not significantly changed by the cold rolling direction. Recrystallization after cold rolling appears to increase the {111} grain orientation on the cold rolled specimen surface.