Analysis of the High Temperature Plastic Deformation Characteristics of 18CrNi4A Steel and Establishment of a Modified Johnson–Cook Constitutive Model

Abstract

To investigate the plastic deformation behavior of 18CrNi4A steel at high temperatures, an isothermal hot compression test was conducted on a Thermecmastor-Z series test machine at deformation temperatures from 1273 K to 1423 K and strain rates ranging from 0.01 s−1 to 10 s−1. The effects of these two factors on the flow stress were analyzed. Based on the true stress–strain experimental curves, the original Johnson–Cook constitutive model was applied to determine the flow stress data under different deformation conditions. The prediction results of the model were compared with the experimental data. The main reason for the large deviation observed between them was that the coupling relationship between the deformation temperature and the strain rate was not considered, so the original Johnson–Cook model was modified. The correlation coefficient and average absolute relative error of the original Johnson–Cook model were 0.962 and 16.36%. The prediction accuracy of the modified Johnson–Cook model was improved to 0.991 and 5.58%, respectively. The results show that the modified Johnson–Cook model exhibits higher prediction precision, which is beneficial for the broader application of 18CrNi4A steel in the industry.