Prediction of hot deformation behaviour of Fe–25Mn–3Si–3Al TWIP steel

Hot deformation behaviour of Fe–25Mn–3Si–3Al twinning-induced plasticity (TWIP) steel was investigated by hot compression testing on Gleeble 3500 thermo-mechanical simulator in the temperature range from 800 to 1100 °C and at strain rate range from 0.01 to 5 s−1, and the microstructural evolution was studied by metallographic observations. The results show that the true stress–true strain curves exhibit a single peak stress at certain strain, after which the flow stresses decrease monotonically until the end of deformation, showing a dynamic flow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be predicted by the Zener–Hollomon (Z) parameter in the hyperbolic sine equation with the hot deformation activation energy Q of 405.95 kJ/mol. The peak and critical strains can also be predicted by Z parameter in power-law equations, and the ratio of critical strain to peak strain is about 0.7. The dynamic recrystallization (DRX) is the most important softening mechanism for the experimental steel during hot compression. Furthermore, DRX procedure is strongly affected by Z parameter, and the decreasing of Z value leads to more extensive DRX.

► Hot deformation activation energy Q of Fe–25Mn–3Si–3Al steel is 405.95 kJ/mol. ► The value of Q is close to that of 304 austenitic stainless steels. ► The peak stress of this steel can be accurately described by Z parameter. ► DRX is the main flow softening mechanism during hot deformation.