Electron Backscattered Diffraction Study of Microstructural Evolution During Isothermal Deformation of High-N Mn18Cr18 Alloy

In order to understand the dynamic recrystallization (DRX) mechanism of Mn18Cr18N austenitic stainless steel during hot deformation, the investigation of microstructure evolution is significant. Isothermal compression tests were conducted on a Gleeble-3500 thermomechanical simulator in the temperature range of 950 °C to 1150 °C and strain rate range between 0.001 and 1 s⁻¹. Optical microscopy (OM) and electron backscattered diffraction (EBSD) were employed to study the resultant microstructures. More grain boundary information of hot-deformed specimens was provided by EBSD. It was found that the fraction of low-angle grain boundaries (LAGBs) increases with the decrease of deformation temperature or the increase of strain rate and can be expressed as a function of the Zener–Hollomon parameter. DRX easily occurs at the high deformation temperature and low strain rate. From the flow stress curves, the occurrence of single peak behavior and multiple transient steady-state (MTSS) behavior illustrated the existence of different DRX mechanisms. The EBSD analysis indicated that both continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) existed during hot deformation. For the low fraction of 10 to 15 deg misorientation, CDRX is the minor DRX mechanism while DDRX is the major DRX mechanism for the studied steel.