Thermodynamic Assessment of Fe–Ni, Fe–C, Ni–C and Fe–Ni–C Systems

Abstract

The liquidus and solidus temperatures of the Fe–Ni system were determined by differential scanning calorimeter. In addition, thermodynamic reassessment of the phase diagrams and thermodynamic properties of Fe–Ni, Fe–C, and Ni–C systems was performed based on literature data and present results. The Gibbs energy of the liquid phase of Fe–C and Ni–C systems was approximated using the association model. The Gibbs energies of the Fcc and Bcc phases were approximated using a two-sublattice model of the (Fe,Ni)₁(C,Va)_0.25 structure. The calculation results were able to reproduce various experimental data. Furthermore, two-phase separation of the Bcc phase in Fe–C and Ni–C at low temperatures were predicted, and this trend is consistent with experimental data. On the other hand, the unreasonable two-liquid separation and the stabilization of the Bcc phase at high temperatures calculated in previous studies were not calculated.

The phase diagrams of the Fe–Ni–C ternary system were also calculated using the parameters of the binary system obtained in this study. All experimental data could be reproduced without introducing ternary parameters. Thus, the model used in this study is suitable for development of a multicomponent database.