Microstructural evolution and constitutive models of 9CrMoCoB heat-resistant steel during high-temperature deformation

In order to research the hot deformation behavior of 9CrMoCoB heat-resistant steel, hot compression tests were performed over a wide range of temperatures from 850 to 1150 °C and strain rates from 0.01 to 10.00 s⁻¹. The flow stress appears to increase with the decrease in deformation temperature and the increase in strain rate. The relationship between microstructural evolution and deformation parameters was studied, indicating that both low strain rate and high deformation temperature appear to promote the dynamic recrystallization, while excessively high temperature with low strain rate would result in the high non-uniformity of grain size. The experimental stress–strain data was applied to calculate the material constants involved in the Arrhenius-type constitutive model and the modified Zerilli-Armstrong (MZA) model, and feasibility of these two models was evaluated. The results show that the MZA model is more accurate to predict the high-temperature flow behavior of the experimental steel than the Arrhenius-type constitutive equation.