C-Mn Thermodynamic assessment

Abstract

The manganese–carbon system has been assessed by means of the CALPHAD method. There is a previous description of this system [W. Huang, Scand. J. Metall., 19 (1990) 26–32], but since then a number of high quality experimental investigations have been published. In addition ab initio calculations of the enthalpies of formation of the manganese carbides have been performed to support the thermodynamic evaluation. The liquid, α-Mn, β-Mn, γ-Mn, δ-Mn and ε-Mn phases are described as solution phases and the carbides Mn23C6, Mn3C, Mn5C2 and Mn7C3 are described as stoichiometric compounds. A good description of most experimental data, in particular the more recent data, has been achieved. The uncertainties in the thermodynamic properties of the stoichiometric carbides and the liquid are quite small, but fairly large uncertainties remain for the phase equilibria and thermodynamic properties of the solid solution phases.