Application of the Quasi-Subsubregular Solution Model

The quasi-subsubregular solution model introduced by Y.-Y. Chuang et al. represents the most complex approach yet to dealing with both compositional and temperature nonregularity in metallic solutions. Evaluation of the model in relation to the Fe-C equilibrium diagram demonstrates that its applicability in dilute solutions is highly dependent on the accuracy of the experimental data from which its coefficients are derived. Lower-temperature equilibria between α-ferrite, austenite, and pure graphite were modeled with reasonable accuracy; the modeling of higher-temperature equilibria in the system was less successful. In particular, experimental difficulties with the measurement of the thermodynamic properties of liquid Fe-C alloys limited the ability of the model to accurately predict the phase diagram. The model can also be used to determine infinite-dilution activity coefficients and to test the adherence of dilute-solution phases to Henrian behavior