Critical evaluations and thermodynamic optimizations of the Mn–S and the Fe–Mn–S systems

Critical evaluations and thermodynamic optimizations of the manganese–sulfur binary system and iron–manganese–sulfur ternary systems have been carried out over the entire composition range from room temperature to above the liquidus temperature. The Gibbs energies of all available phases have been thermodynamically modeled, and model parameters have been optimized in order to reproduce all available and reliable experimental data simultaneously within experimental error limits. For the liquid phase, the Modified Quasichemical Model (MQM) in the pair approximation is employed in order to properly take into account short-range-ordering in the phase. Thermodynamic model parameters of binary liquid Fe–S using the MQM and those of binary liquid Fe–Mn using the random-mixing model available in the literature are combined with those of binary liquid Mn–S using the MQM from the present study, in the framework of the MQM, in order to estimate Gibbs energy of ternary liquid Fe–Mn–S. Observed ternary solid solutions: (Mn, Fe)S and Fe 1 − x S are modeled using simple random-mixing model.