Investigation on Post-Deformation Recrystallization Behavior of 22MnB5 Steel based on Stress Relaxation

Abstract

With the aim of analyzing the post-deformation Recrystallization (PDRX) of 22MnB5 steel and the grain size evolution after hot forming of the sheet and using the BAEHR 805 A/D thermo-mechanical simulator, several isothermal stress relaxation tests were performed in a temperature range of 800 to 950 °C, a predeformation range of 0.4 to 0.8 and a strain rate range of 0.01 to 0.8 s−1. As a result of isothermal stress relaxation after deformation, PDRX kinetics can be described based on an Avrami equation as a function of temperature, degree of predeformation and strain rate. As the temperature increases, the recrystallization kinetics accelerates. The strain rate also has a positive influence on the fast PDRX. Predeformation has the opposite effect, as the consumption of stored energy occurred in predeformation process of relaxation tests. Furthermore, the microstructure evolution is described as a function of the predeformation parameters. The investigation of the microstructure after isothermal stress relaxation tests showed that the PDRX kinetics corresponds to the calculations. Furthermore, EBSD analysis helped to analyze the effects of certain stress relaxation conditions on the martensite morphology. The results indicate that a lower temperature and higher strain rate lead to fine martensite packages. In contrast, the martensite block width increases when applying higher strain rates.