Hot working processing and microstructure characterisation of as-cast high manganese TWIP steel

The hot compression of the as-cast Fe-21Mn-0.7C-0.1Si twinning induced plasticity (TWIP) steel was investigated at the deformation temperature range of 950-1100 degrees C and strain rates of 0.01-5 s(-1), using a Gleeble (TM) thermo-mechanical simulator, to determine the hot deformation behaviour and analyse the recrystallisation mechanism. The results showed that the flow curves were characterised by yield-point-elongation (YPE) and dynamic recrystallisation (DRX) as the principal restoration mechanisms. The activation energy (Q) was calculated to be 394.975 KJ mol(-1), which implies that the recrystallisation is sluggish in the whole range of the deformation conditions. Furthermore, the processing maps were generated according to the dynamic material model (DMM). The processing map was subdivided into different domains for the microstructural observations. The ideal hot deformation parameters of as-cast high Mn TWIP steel were obtained in the deformation condition range of 1087-1098 degrees C/10(-1.2)-10(-0.17) s(-1). Moreover, the microstructure analysis revealed that the DRX grains were twinned and nucleated through the bulging mechanism at the serrated grain boundaries, accompanied by twin boundaries migration created in the DRX grains by growth accidents, which contributed significantly to the growth of the DRX.