In-situ observations and modeling of static recrystallization in 300 M steel

Abstract

The study of static recrystallization (SRX) has been widely concerned for its importance in regulating the microstructure and mechanical properties of deformed materials. In the paper, the effects of SRX on the flow behaviors of 300 M steel are investigated by thermal compression experiments. The SRX mechanism of 300 M steel is investigated by high temperature laser scanning confocal microscopy (HTLSCM) setup. The variations in the flow behaviors and microstructure under different experimental conditions are discussed in detail. Also, the relationships between microstructure evolution and mechanical properties are analyzed. The SRX mechanism is detected by the analysis of microstructure. According to the statistical results of microstructure, the SRX kinetics models and the average recrystallization (RX) grain size model are proposed. It can be found that the flow stress increases with the increased strain rate and reduced deformation temperature. The yield stress is affected by both the softening mechanisms of static recovery and SRX. The main SRX mechanism of 300 M steel is strain-induced boundary migration (SIBM). Compared to the pre-strain rate, the insulation temperature has a more significant effect on the SRX rate, maximum SRX volume fraction and average RX grain size. And the effects of pre-strain rate on the RX grain size are negligible at low pre-strain rate. The comparison between the calculated and experimental results is consistent, which implies that the established models can describe the SRX process accurately. Besides, compared to the softening volume fraction calculated based on the stress-strain curves, the SRX volume fraction calculated based on the statistic results of microstructure can reflect the SRX process more precisely, which indicates the effectiveness of the research method used in the paper.