Thermodynamic modeling of the Pt-Zr system

By means of the CALPHAD (CALculation of PHAse Diagram) technique, the Pt-Zr system was critically assessed. The solution phases (liquid, bcc, fcc and hcp) are described with the substitutional model. The intermetallic compounds Pt4Zr, Pt4Zr3, αPtZr and Pt3Zr5 are treated as the formula (Pt,Zr)m(Pt,Zr)n by a two-sublattice model with the elements Pt and Zr on the first and the second sublattices, respectively. A two-sublattice model (Pt,Zr)0.5(Pt,Zr)0.5 is applied to describe the compound βPtZr with CsCl-type structure (B2) in order to cope with the order-disorder transition between bcc solution (A2) and βPtZr (B2). Another two-sublattice model (Pt,Zr)0.75(Pt,Zr)0.25 with Ni3Ti-type structure (D024) is applied to describe the compound Pt3Zr in order to cope with the order-disorder transition between hexagonal close-packed (A3) and Pt3Zr (D024). The compound Pt10Zr7 is treated as a stoichiometric compound. A set of self-consistent thermodynamic parameters of the Pt-Zr system was obtained. (orig.)