Experimental investigation and thermodynamic modeling of the Nd-Ni system

The Nd-Ni system has been investigated via experiments and thermodynamic modeling. In the experimental part, alloys across the entire composition range were prepared by arc melting pure Nd and Ni slugs and annealing the alloys at 500 °C (<70 at.% Ni) and 800 °C (>70 at.% Ni) for 2 weeks. The annealed alloys were then subjected to differential scanning calorimetry and differential thermal analysis (DTA) measurements to determine the invariant reaction temperatures. Except for the peritectic reaction liquid + Nd7Ni3 ↔ Nd3Ni and the polymorphous phase transformation of Nd2Ni7 found in this study, all the other invariant reactions are confirmed to be the same types but with significant different temperatures as reported results. In the modeling part, the available phase equilibrium and thermodynamic data in the Nd-Ni system were analyzed by using thermodynamic models for the Gibbs energies of individual phases. An optimal set of thermodynamic parameters were obtained using WinPhad software. The calculated phase equilibria and thermodynamic properties from the model parameters were compared to the corresponding experimental data and good agreement was obtained.