Some phase-diagram aspects of the manganese-carbon system

In the present work, differential thermal analysis (DTA) and electromotive force (emf ) methods were employed to investigate the Mn-C phase diagram around the eutectoid decomposition of Mn(γ). The eutectoid temperature and the composition were estimated to be 1031 K and 9.62 mol pct carbon, respectively. The temperature for the eutectoid decomposition of ε-carbide to Mn(γ) and Mn₂₃C₆ was found to be 1260 K, and the equilibrium composition of Mn(γ) corresponding to this three-phase reaction was 14.89 mol pct carbon. From the experimental data, the solubility of Mn₂₃C₆ in Mn(γ) was evaluated in the temperature range of 1031 to 1260 K using a two-sublattice model. On the basis of the present results, the relevant part of the Mn-C diagram was redrawn. Microscopic and X-ray analyses of quenched samples appear to be in support of the suggested phase diagram.