A thermodynamic assessment of the Iron+Holmium phase diagram

The thermodynamic modelling of the Iron+Holmium binary system was carried out with the help of the CALPHAD (CALculation of PHAse Diagram) method. The four intermediate phases Fe17Ho2, Fe23Ho6, Fe3Ho and Fe2Ho have been treated as stoichiometric compounds while a solution model has been used for the description of the liquid phase and the (Fe) and (Ho) solid solutions. The excess term of the Gibbs free energy of the solution phases was assessed with the Redlich-Kister (Redlich and Kister, 1948) [1] polynomial equation. The calculations based on the thermodynamic modelling are in good agreement with the phase diagram data and experimental thermodynamic values available in the literature.