Constitutive Modeling for Flow Stress and Processing Maps of a 0.2C–2.0Mn–0.5Cr Microalloyed Steel

Abstract

Low‐carbon microalloyed steel with the microstructure of bainite is frequently utilized to produce automotive parts. The systematic investigation of the hot deformation behavior can serve as a reference for the optimization of deformation process parameters. The hot deformation of 0.2C–2.0Mn–0.5Cr microalloyed steel is studied. Based on the stress–strain curve, an Arrhenius model with strain compensation is established. The correlation coefficient R2 and the average absolute relative error calculated according to this model are 0.962 and 4.871%. The microstructure evolution at the strain of 0.90 is studied. In the stable region with substantial power dissipation, the microstructure is uniformly fine. The strain rate is high in the stable region with low‐power dissipation, and the room‐temperature microstructure after deformation retains a large amount of deformation storage energy and fine substructures. During deformation, the banded structures are formed in the instable region. The difference in dislocation density between the band structure and the nearby regions promotes the formation of necklace microstructures. Therefore, the 0.2C–2.0Mn–0.5Cr microalloyed steel has an ideal deformation process window in the range of a hot deformation temperature of 880–920 °C and a strain rate of 0.1–0.3 s−1.