Thermal deformation behavior and microstructure analysis of the as-cast super austenitic stainless steel Sanicro35

Abstract

Thermal compression experiments on the super austenitic stainless steel Sanicro35 were carried out using a Gleeble 3800 thermal simulation laboratory machine to investigate its thermal deformation behavior at different deformation temperatures (900 °C–1150 °C) and strain rates (0.001–10 s−1). The microstructure of the large deformation zone of the specimen was investigated using electron backscatter diffraction (EBSD). The results show that the thermal compression rheological stress of the super austenitic stainless steel Sanicro35 decreases with increasing temperature and decreasing strain rate. Dynamic recrystallization (DRX) is the main softening mechanism for this material. The morphology characteristics, recrystallization fraction, dislocation density and twin grain boundary distribution of the microstructure were analyzed by EBSD. With the increase of deformation temperature, the higher grain boundary mobility contributed to the growing of DRX grains. As the strain rate increases, the larger deformation storage energy provides sufficient activation energy for DRX grain nucleation, and the nucleation of DRX grains becomes denser. The twin boundaries are mainly distributed within the DRX grains. The smaller the grain size of DRX, the denser the nucleation of twin boundaries, and the generation of twins can promote the development of DRX. The softening mechanism under most deformation conditions is discontinuous dynamic recrystallization (DDRX). However, at 10 s−1, the high strain rate causes microbands to be generated within the deformed grains, and the microband boundaries evolve toward the high-angle grain boundaries (HAGBs) with increasing temperature, which promotes the occurrence of Continuous dynamic recrystallization (CDRX).