The microstructural evolution of a cold-rolled steel 0.1C–5Mn was characterized by SEM and EBSD, and the αγ phase transformation of the steel was determined by differential scanning calorimetry (DSC) upon heating. The retained austenite fraction and the dislocation density were examined by XRD. Based on the DSC data, the Kissinger?s method was used to calculate the activation energy of the cold rolled steel. The activation energy of 363–824 kJ/mol suggested a sluggish phase transformation during the heating process and it showed an increase trend with the increase of thickness reduction which was affected by the density of the dislocation and the drag effect by the solute Mn. The stored energy (14–30 J/g) was associated with energy released from the αγ transformation during the heating process. Based on the effects of temperature on the phase transformation behavior, the cold rolled medium-Mn steel with different thickness reductions were annealed at the onset phase transformation temperature with 5 min and 6 h, which results in a very good combination strength and ductility.

This paper was originally published in Materials Science and Engineering: A 636 (2015) 108–116

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