Hot working process optimization of Fe–20Mn–19Cr–0.5C–0.6N steel by activation energy, power dissipation and microstructural evolution

Hot deformation behavior of an Fe–20Mn–19Cr–0.5C–0.6N high-nitrogen austenitic steel has been studied by isothermal compression tests in deformation temperature range of 800–1200 °C and strain rate range of 0.01–10 s −1 . Results indicate that the Fe–20Mn–19Cr–0.5C–0.6N steel has high deformation resistance due to strong hindering effect on dislocation moving by nitrogen-induced lattice misfit. The twinning-induced plasticity effect is gradually suppressed with the increase in deformation temperature, and high-temperature plastic deformation mechanism by twinning is gradually replaced by dislocation planar slip. The deformation resistance is up to 343 MPa at deformation conditions of (1000 °C, 0.01 s −1 ), which is over 100 MPa higher than that in martensitic steel and 50 MPa higher than that in austenitic steel. Besides, value of deformation activation energy for the Fe–20Mn–19Cr–0.6N steel is up to 784 kJ mol −1 . Power dissipation efficiency is lower than 0.13, while hot processing map exhibits a very wide range of working area. The optimum hot working process obtains at deformation temperature range of 950–1200 °C and strain rate range of 0.01–10 s −1 , when deformation activation energy is less than 662.6 kJ mol −1 , power dissipation efficiency exceeds 0.22, dynamic recrystallization fraction is over 46.1% and microstructures are without instable characteristics.