Deformation behavior and softening mechanism in ferrite steel during warm deformation

Ferrite rolling is generally used to produce deep-drawn steel sheets, which can replace cold rolling to achieve short-flow production. Realizing low-cost production of deep-drawn steel. However, the deep-drawn performance of ferrite rolling products is not as good as the deep-drawn performance of cold rolled products. Of which dynamic recrystallization microstructure have a great effect on the deep-drawn performance. In the present study, ferrite steel was compressed at different deformation parameters (including deformation temperatures and strain rates) in a thermo-mechanical testing system to simulate the deformation behavior during the ferrite regions. The flow behavior of the ferrite steel was studied, and processing maps of the ferrite steel were plotted. The relationship between the Zener-Hollomon parameter and the dynamic recrystallization mechanisms of the ferrite steel was studied in this paper. The microstructure evolution in the steel was characterized by optical microstructure, electron backscatter diffraction, and transmission electron microscopy. The results show that both dynamic recovery and dynamic recrystallization happened during deformation process. The main softening mechanism was dynamic recovery. Discontinuous dynamic recrystallization, continuous dynamic recrystallization and geometric dynamic recrystallization were found in ferrite steel. Meanwhile, it was found that a corresponding relationship between dynamic recrystallization mechanisms and ln Zener-Hollomon values. At high ln Zener-Hollomon value, the dynamic recrystallization mechanism was discontinuous dynamic recrystallization. At middle ln Zener-Hollomon value, the dynamic recrystallization mechanism was continuous dynamic recrystallization. At low ln Zener-Hollomon value, the dynamic recrystallization mechanism in addition to continuous dynamic recrystallization and geometric dynamic recrystallization.