Microstructure evolution and constitutive equations for the high-temperature deformation of 5Cr21Mn9Ni4N heat-resistant steel

The high-temperature deformation behavior of 5Cr21Mn9Ni4N heat-resistant steel was studied using a Gleeble-1500D thermal simulation test machine for high-temperature compression tests. The deformation temperatures ranged from 1273 K to 1393 K, and the strain rates ranged from 0.1 s−1-10 s−1. The height reductions were 20%, 40%, and 60%. The flow stress of 5Cr21Mn9Ni4N increased with increasing strain rate, whereas it decreased with increasing temperature. The high-temperature deformation of 5Cr21Mn9Ni4N began from the strain-hardening stage to the steady-state deformation stage. The characteristics of the stress-strain curves were determined through the interaction of work hardening, dynamic recovery, and dynamic recrystallization. The relationship between microstructure and processing parameters was analyzed. A set of unified viscoplastic constitutive equations based on changes in dislocation density, volume fraction of dynamic recrystallization, and grain size was established to predict deformation behavior and microstructure during a high-temperature working process. The average relative error between the calculated and experimental flow stress was 4.8%. This finding indicated that the constitutive equations could be used to predict the flow behavior of 5Cr21Mn9Ni4N accurately during high-temperature deformation.