A thermodynamic assessment of the iron–yttrium system

•Rare earth elements are increasingly used in advanced materials (permanent magnets, hydrogen storage alloys, luminescent materials…).•To our knowledge, this system was not previously optimized.•Two formalisms were compared for the excess terms of the solution phases.•A consistent set of thermodynamic parameters was optimized (good agreement between calculation and experiments).•This work is the start point for the study of ternary systems with RE. The thermodynamic modeling of the Iron–Yttrium binary system was carried out with the help of the CALPHAD (CALculation of PHAse Diagram) method. The excess term of the Gibbs energy of the solution phases (liquid, b.c.c., f.c.c. and h.c.p.) was assessed with the recent exponential temperature dependence of the interaction energies by Kaptay [1–3] and compared with the linear temperature dependence of Redlich–Kister [4] polynomial equation results. The intermetallic compounds Fe23Y6 and Fe2Y in this binary system which have a homogeneity range, were treated by a two-sublattice model with convenient substitution in each sublattice [5,6]. The others were considered as stoichiometric compounds. A consistent set of thermodynamic parameters leading to a reasonable agreement between the calculated results and literature data was obtained for this system which has not been previously optimized.