Thermodynamic modeling of the Co–Sm system

The phase diagram of the Co–Sm system has been assessed by applying the Calculation of Phase Diagram (CALPHAD) technique. Thermochemical and phase equilibrium information from the literature have been critically evaluated, and a series of self-consistent thermodynamic parameters capable of describing the Gibbs free energies of each phase of the system has been obtained. There are eight compounds in this system. Based on an analysis of experimental data and the crystal structures of the phases, SmCo5 was modeled as (Co,V a)0.833333(Co2,Sm)0.166667 and Sm2Co17 as (Co)0.833333(Sm)0.111111(Co2,Sm)0.055556. The remaining six intermetallic phases, Sm3Co,Sm9Co4, SmCo2, SmCo3, Sm2Co7, and Sm5Co19, were treated as stoichiometric compounds. Calculations based on these parameters can reproduce most of the experimental data very well.

► The Co–Sm system has been re-assessed using the latest experimental results.
► The solubilities of SmCo5 and Sm2Co17 were considered here for the first time.
► The errors of related modeling presented in previous articles have been modified.
► A self-consistent thermodynamic description of the Co–Sm system was obtained.