Gibbs energies of formation of Mn 3C, M(Fe, Mn) 3C and Mn 23C 6 from the ternary phase equilibria in the FeMnC system

Abstract

The high temperature phase relations in the FeMnC system have been analyzed in light of the recently developed thermodynamic method by the authors to obtain the Gibbs energies of formation of Mn 23C 6 and Mn,C. A new thermodyn/amic treatment is outlined and applied to obtain the stability of the ternary carbide M(Fe,Mn) 3C without any a priori assumption of a solution model for the M 3C phase. The recommended Gibbs energies of formation for the Mn carbides, Mn 3C and Mn 23C 6 With γ-Mn (graphite) as the Standard states are: Δ G 0 Mn 3 C =−16.9−0.015 T kJ 1243≤ T≤1323 K Δ G 0 Mn 23 C 6 =−133.7−0.090 T kJ 873≤ T≤1273 K The present method can be extended to obtain a consistent set of thermodynamic data for binary and ternary carbides from various ternary metal-metal-carbon phase relations.