Modeling of Metadynamic Recrystallization Kinetics and Recrystallization Mechanisms of V-Containing 12Cr Rotor Steel

Abstract

In order to study the metadynamic recrystallization (MDRX) behavior of 12Cr rotor steel, the double-hit hot compression tests were performed on a Gleeble1500D thermal simulator with temperatures of 1273-1373 K, strain rates of 0.001-0.05 s 21 and inter-pass times of 5-60 s. Based on the true stress-strain curves obtained at different deformation conditions, the effects of different deformation parameters on the MDRX softening behavior are discussed. Meanwhile, the microstructure was observed using an optical microscope, electron backscatter diffraction and transmission electron microscopy. Analysis showed that recovery was the main softening mechanism, followed by recrystallization. And the bulging at the grain boundary was the fundamental nucleation mechanism for MDRX. Furthermore, the kinetics model for MDRX of 12Cr rotor steel was established, which was verified to have an accurate capability of predicting MDRX softening behavior with a correlation coefficient of R = 0.9956.

Quantification of static softening process and its effects on work hardening characteristics of a typical high strength steel during multi-pass deformation

“…t 50 srx is the time corresponding to 50% SRX fraction, and can be calculated by equation (5) [41,44]: ~are the material constants, d 0 is the initial grain size of experimental material, and Q s is SRX activation energy. The form of the MDRX kinetics model is similar to the SRX kinetics model [10]. The distinction between the SRX and MDRX kinetics models lies in the material constants.…”

“…Equation (10) displays the calculated results. According to equation (10), strain has the most significant influence on the static softening process of 300 M steel, followed by holding time, and then the deformation temperature, while strain rate has the weakest influence.…”

“…Zhang et al [9] studied the effects of deformation temperature and holding time on the static recrystallization (SRX) softening behaviors of pure molybdenum, and established a SRX kinetics model. Xu et al [10] explored the effects of different deformation and inter-pass holding parameters on the metadynamic recrystallization softening (MDRX) behaviors of V-containing 12Cr rotor steel, and constructed an MDRX kinetics model. Nie et al [11] investigated the effects of the static softening process on the hot workability of Mg-8Gd-3Y alloy during multi-pass deformation, and found the inter-pass holding process can widen the processing windows.…”