Abstract:On the basis of the experimental data of phase equilibria and thermochemical properties available from literatures, a critical assessment for the Ni-Yb binary system was carried out using the CALPHAD (calculation of phase diagrams) method. The liquid phase is modeled as the associate model with the constituent species Ni, Yb and YbNi₃, owing to the sharp change of the enthalpy of mixing of liquid phase at the composition of around 25% Yb (mole fraction). The terminal solid solutions FCC_A1 (Ni/Yb) and BCC_A2 (Yb) are described by the substitutional solution model with the Redlich-Kister polynomial. The intermetallic compounds, Yb₂Ni₁₇, YbNi₅, YbNi₃, YbNi₂, α-YbNi and β-YbNi, are treated as strict stoichiometric compounds, since there are no noticeable homogeneity ranges reported for these compounds. A set of self-consistent thermodynamic parameters for the Ni-Yb binary system are obtained. According to the presently assessed results, the thermochemical properties and the phase boundary data can be well reproduced.

Key words: Ni-Yb system; thermodynamic assessment; CALPHAD technique