Optimization and calculation of the Hf-Ni phase diagram

Abstract

An optimized phase diagram for the Hf-Ni system was constructed using experimental data from the literature. The excess free energies of solution phases, liquid and (Ni) were described by the Legendre polynomials. Eight compounds, i.e. Hf 2Ni, HfNi, Hf 9Ni 11, Hf 7Ni 10, Hf 3Ni 7, HfNi 3, Hf 2Ni 7 and HfNi 5, were modelled as line compounds. Two terminal solid solution phases, i.e. β-Hf and α-Hf, were treated as pure elements b.c.c.-Hf and h.c.p.-Hf respectively. Optimization and calculation were performed alternatively with different selections of data in the composition region 15–50 at.% Ni in order to get the most acceptable compromise between the conflicting experimental results. The data set obtained was subjected to adjustment by systematic trial and error in the ranges of 15–50 and 90–100 at.% Ni where the experimental data were insufficient for a reasonable calculation.