Austenite Thermal Stabilization through the Concentration of Manganese and Carbon in the 0.2C–5Mn Steel

Formation of the reversed austenite by intercritical annealing has been studied in the 0.2C–5Mn steel by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the volume fraction of reversed austenite increases solely with increasing annealing temperature. While the volume fraction of retained austenite begins to go up around 575°C and exhibits a maximum value of 33.0% at 650°C; and when above 650°C, the retained austenite volume fraction decreases with increasing annealing temperature. At the same time, the concentrations of C and Mn in austenite which contribute a lot to the thermal stabilization of austenite are investigated to explain the variation of retained austenite volume fraction. And the microstructure evolution of different annealing temperatures is also observed.