Dynamic recrystallization and constitutive equation of 15Cr-10Mn-Ni-N steel under hot deformation

Abstract

Hot working as one of the indispensable processes for all metal materials can effectively refine the grain to improve the material properties. However, the study on the hot-deformation process of low-Ni austenitic stainless steel is scarce. In this study, we conducted single-pass compression tests to explore the dynamic recrystallization process of a low-Ni austenitic stainless steel with the chemical compositions of 15Cr-10Mn-Ni-N during deformation at various temperatures and strain rates. According to the experimental data, the true stress-strain curves are drawn and constitutive equation is established to predict the variations of stress and strain, accompanied with high accuracy. The microstructural characterizations show that the increase of deformation temperature leads to the occurrence of recrystallization in spite of the enhanced softening effect. In particular, the increase of strain rate promotes the refinement of grain size, and the average grain size significantly decreases from 200 µm to 20 µm under the compression condition of 1100 ℃ and 10 s−1. The decreasing grain size can compensate the sacrificing strength due to the reduction of Ni addition. The peak stress of 15Cr-10Mn-Ni-N austenitic stainless steel is 186 MPa at 1000 °C and 0.1 s−1, which is basically similar with the conventional austenitic stainless steel. Evidently, the austenitic stainless steel in this study has a cost-effective advantage because of its low Ni addition, i.e., we have the advantage of reducing material costs while maintaining the identical mechanical properties. Here the recrystallization process of 15Cr-10Mn-Ni-N austenitic stainless steel provides a basis for the selection of thermal processing parameters and a general understanding of the microstructure evolution.