Study on Dynamic Recrystallization Behaviors in a Hot-Deformed FB2 Ultra-supercritical Rotor Steel

In the present work, hot deformation behaviors of FB2 ultra-super-critical rotor steel are investigated by isothermal compression tests under the deformation temperature range of 1323-1473K and strain rate range of 0.01-1s(-1). The microstructure evolution of the deformed samples and the nucleation mechanism of dynamic recrystallization are studied by using electron backscatter diffraction and transmission electron microscopy. The results show that: (1) when the strain rate is higher than 0.1s(-1) and the temperature is lower than 1373K, it easily results in a large number of substructures with relatively low-angle boundaries due to the intense work hardening effect. (2) Discontinuous dynamic recrystallization characterized by grain boundary bulging is the dominant nucleation mechanism for the studied rotor steel. (3) Geometrically necessary dislocations are sensitive to strain rate for the studied rotor steel but is less sensitive to the deformation temperature. (4) The low-angle boundaries fraction slightly increases with the increase in the Zener-Hollomon (Z) parameter under the test conditions.