The influence of manganese on kinetics of austenitization of the Fe-Mn-C ternary alloys

The influence of manganese on the microstructure and kinetics of the austenization in the Fe-Mn-C ternary alloys, which contains four grades of Mn concentration, is studied under continuous heating. The transformation of the pearlite-austenite has been measured by differential scanning calorimetry (DSC) in temperatures that ranged from room temperature to 1373 K. Also, the microstructure of the as-cast and the completion of the DSC test is obtained using optical microscopy (OM) and scanning electron microscopy (SEM), respectively. The analysis of the microstructure indicates that the lamellar spacing of the initial pearlite is refined from 0.34 jtm to 0.19 jtm. It also indicates that austenite grain coarsening occurs as Mn concentration increases. The comparison of experimental kinetic curves and the Johnson-Mehl-Avrami-Kolmogorov model (JMAK) shows that the start temperature of austenization is decreased from 1010.5 K to 999.28 K. and that the austenite formation rate is accelerated. Moreover, the activation energy of diffusion decreases from 192.88 kJ mol(-1) to 178.47 kJ ma', and the pre-exponential factor decreases from 5.32 x 10(-3) m(2)s(-1) to 3.1 x 10(-3) m(2) s(-1).