Hot deformation of alumina-forming austenitic steel: EBSD study and flow behavior

The flow behavior of alumina-forming austenitic steel was studied using axisymmetric hot compression on a Gleeble-3500 thermomechanical simulator. The temperature range was 900–1200 °C, and strain rate range was 0.1–100 s−1. The microstructures after deformation were investigated by electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The deformation temperature and strain rate have a significant influence on the flow stress. A constitutive equation, describing the flow stress as a function of deformation temperature and strain rate, has been developed, and the hot deformation activation energy was confirmed as 579.4 kJ/mol. Dynamic recrystallization (DRX) progress had been finished after increasing hot deformation temperature to 1100 °C at a strain rate of 100 s−1, leading to the obvious transformation from low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs), and a relatively stable fraction of HAGBs was obtained. At a strain rate of 100 s−1, the β-fiber at {011} transited to {112} (C orientation), and finally a recrystallized orientation of {100} formed after absolute DRX. GDRX is the primary DRX mechanism, but DDRX mechanism is dominant with the increase in deformation temperature at a high strain rate of 100 s−1.