Hot deformation behavior of a cryogenic high manganese steel based on the microstructure and texture evolution

Abstract

The correlation between microstructure evolution, texture development and hot deformation behavior of high manganese steel for LNG were investigated through uniaxial hot tensile tests at different temperatures (800, 850, 900 and 980 °C). Hot tensile tests were carried out on a Gleeble 3800 thermomechanical simulator with a strain rate of 10 /s. Texture analysis was conducted by the orientation distribution functions acquired from the electron backscatter diffraction (EBSD). Detailed microstructure and dynamic recrystallization (DRX) were indicated by the grain orientation spread of EBSD and transmission electron microscopy (TEM). The results show that there are only two stages in the work hardening rate when the deformed microstructure is non-recrystallized or mostly recrystallized. The work hardening rate exhibits a wave-like fluctuation when the tensile temperature is near the critical DRX temperature, due to the continuous competition between the dislocation packing caused by deformation and the softening intrigued by DRX. The deformed microstructure contains the highly dense dislocation wall (HDDW) structure and the cell block structure, and the HDDW structure mostly occurs in the 〈001〉//td fiber while the latter corresponds to the 〈111〉//td fiber. What's more, <001>//td fiber has stronger orientation gradient and work hardening rate than <111>//td fiber. DRX preferentially nucleated on the <001>//td fiber through two nucleation methods: strain-induced grain boundary migration and twining nucleation. DRX grains only retain the weak {111} 〈112〉 F and {110} <112> A textures, and the overall texture was weakened and randomized.