Recent studies on thermophysical properties of metallic alloys with PROSPECT: Excess properties to construct a solution model

We have developed the system PROSPECT for measuring thermophysical properties at high temperature. Precise thermophysical measurements provide accurate excess functions, which represent non-ideality of solutions. We use excess functions to discuss solution models on the basis of electronic structure and thermodynamics. Pd-Fe systems show positive excess volume VE with negative excess Gibbs energy GE. The phase diagrams of these systems have common features with those of other Pd-X and Pt-X systems (where X is Fe, Ni, Co, or Cu), which means they all have order-disorder transitions. The correlation between VE and GE is discussed in terms of the electronic structure of the alloys, and an energy diagram is proposed to understand this correlation. The excess heat capacity CpE of Fe-Ni melts is positive over a whole composition range and a wide temperature range. We estimate the temperature dependences of the excess enthalpy HE and excess entropy SE of Fe-Ni melts from CpE. The Lupis-Elliott rule is satisfied for HE and SE with positive CpE.