Thermodynamic Assessment of Liquid Fe-Ni-C Alloy Using Modified Quasichemical Model

The liquid solution properties in the Fe-Ni and Fe-Ni-C systems have been thermodynamically assessed using the modified quasichemical model in the pair approximation. The asymmetry of the Fe-Ni and Fe-Ni-C alloy melts was verified by measuring the melting points of Fe-Ni binary alloys on the Ni-rich side, and the C solubility limit in Fe-Ni melt over the entire concentration range at 1500°C and 1600°C. The solubility minimum of C and the maximum partial enthalpy of mixing of C in the ternary Fe-Ni-C system occurred at near the maximum short-range ordering composition of the binary Fe-Ni liquid solution. The extrema of the partial properties of C in the ternary Fe-Ni-C system were successfully reproduced with only one constant adjustable ternary parameter.

“Constant-Volume Alloy” Formulation of Enthalpy of Mixing for Metallic Systems

We present an exact statistical thermodynamic expression for the partial enthalpy of mixing for metals which avoids the problems of evaluating the large internal energy of the pure metals from the plasma state. This method is applied to the homovalent alloys Al-Ga, Al-In and Al-Tl. The results show clearly the tendency towards a critical mixing point in these systems when using a pseudopotential theory for these metals. An estimate for the critical point of the Al-Tl system and reasonably correct values for the partial enthalpies at infinite dilution are obtained.