Arrhenius constitutive model and dynamic recrystallization behavior of 18CrNiMo7-6 steel

In order to analyze the thermal deformation and dynamic recrystallization behavior of 18CrNiMo7-6 steel, the isothermal compression tests are carried out on Gleeble-3500 thermal simulator machine at deformation temperatures 973.15 K-1273.15 K with strain rates 0.001 s-1-1 s-1. Based on the true stress s0.3, the Arrhenius constitutive models are constructed by using characterization parameters and physical base parameters, and the determination coefficients between the predicted values of the two models and the measured values are 0.98378 and 0.97613, respectively. The constitutive models of char-acterization parameters and physical base parameters considering strain effect are also constructed, and a comparative analysis is made. The results show that the predicted values of the characterization parameters constitutive model is closer to the measured values in the low strain region. After reaching the peak strain, the predicted values of the two constitutive models are close to the measured values, and both have high prediction accuracy. The dynamic recrystallization models are established to characterize the recrystallization behavior. The recrystallization activation energy of 18CrNiMo7-6 steel is 169.6793 kJ mol-1, the ratio of critical strain to peak strain is about 0.47074, and the ratio of critical stress to peak stress is about 0.94059. The activation energy of 50% dynamic recrystallization is 29.9844 kJ mol-1. The dynamic recrystallized grain size increases with increasing deformation temperature or decreasing strain rate, and the activation energy of grain growth is -49.9237 kJ mol-1.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In order to analyze the thermal deformation and dynamic recrystallization behavior of 18CrNiMo7-6 steel, isothermal compression tests were conducted at different deformation temperatures and strain rates. The constitutive models based on true stress were constructed and validated, and the models considering strain effect were also compared. The results showed good accuracy of the models and revealed the recrystallization behavior and grain growth characteristics of the steel.