Thermodynamic Functions of Undercooled Fe–P Melts

The approaches to calculating the thermodynamic properties of undercooled melts are critically evaluated. It is shown by the example of the eutectic Fe–P alloy that the rough estimates relying on various models of melt structure, primarily on the hole theory, provide inadequate results. Based on the concept of associated solutions and the thermodynamic functions of the constituent components found by solving the inverse problem of chemical thermodynamics, a procedure is proposed for analyzing the thermodynamic behavior of undercooled melts, in particular, near the glass transition. The thermodynamic quantities calculated by this procedure coincide with experimental data to within the measurement accuracy. The procedure is used to calculate the thermodynamic properties and viscosity of Fe–P melts between the glass-transition temperature (≃650 K) and 1873 K. The results are in perfect agreement with experimental data.