Experimental determination and thermodynamic calculation of phase equilibria in the Sm-Fe-B ternary system

The phase equilibria of the Sm-Fe-B ternary system at 873 K and 1073 K were experimentally investigated by equilibrated alloy method using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Four ternary intermetallic compounds, Sm₂Fe₁₄B with a Nd₂Fe₁₄B-type structure and space group P4₂/mnm, Sm₁₇(Fe₄B₄)₁₅ with a RE_l.1Fe₄B₄-type structure and space group P4₂/n, SmFeB₄ with a YCrB₄-type structure and space group Pbam and Sm₅Fe₂B₆ with a Pr₅Co₂B₆-type structure and space group $R\bar{3}m$ , were confirmed by the SEM-EDS results and the XRD Rietveld refinements. The isothermal sections of this ternary system at 873 K and 1073 K were established. Furthermore, in the combination with the previous assessments of the Sm-Fe, Sm-B and Fe-B binary systems and the measured and reported experimental results, thermodynamic calculation of the Sm-Fe-B ternary system was performed using the CALPHAD method. The calculated isothermal sections at 873 K and 1073 K are in good agreement with the determined experimental results. Thermodynamic parameters of the Sm-Fe-B ternary system were obtained finally, which would provide a good basis for the development of a thermodynamic database of RE-Fe-B-based magnetic alloys.