Thermodynamic modeling of the Ru–Zr system

The Ru–Zr system has been critically assessed by means of the CALPHAD technique. Based on the experimental data, the solution phases (liquid, body-centered cubic, hexagonal close-packed) were initially modeled with the Redlich–Kister equation. It was shown that this model had a definite temperature range beyond which the liquid became unstable. To tackle the problem, the solution phases were modeled with a new semi-empirical equation, which was recommended by Kaptay. A two-sublattice model (Ru, Zr)0.5(Ru, Zr)0.5 is applied to describe the compound RuZr in order to deal with the order–disorder transition between body-centered cubic solution (A2) and RuZr with CsCl-type structure (B2). Another two-sublattice model (Ru, Zr)0.6667(Ru, Zr)0.3333 is applied to describe the compound Ru2Zr in order to cope with the order–disorder transition between hexagonal close-packed (A3) and Ru2Zr with MgZn2-type structure (C14). A set of self-consistent thermodynamic parameters of the Ru–Zr system was obtained.