Modified general solution model for interstitial solid solution

By introducing two sublattices to the general solution model, a modified model for studying the thermodynamic properties of interstitial solid solutions in multicomponent steels is suggested. The excess Gibbs free energy of mixing in Fe-Σi-C steel can be calculated from the modified model with the thermodynamic parameters of ternary Fe-i-C and binary i-j systems that are easily obtained. As an example, Ae3 temperatures for pro-eutectoid ferrite formation in nine steels have been calculated from the modified general solution model and compared with that from the two-sublattice model using the interactions among multicomponents or not and that from ThermoCalc software. The relative standard deviation and root-mean-square error between the experimental Ae3 temperatures and the values calculated from the modified model are 0.57% and 7.2K, respectively. It can be concluded that the modified general solution model for interstitial solid solutions is acceptable.