Phase equilibria, phase structure and phase transition of Y-Fe-B alloys: Experimental investigation and thermodynamic calculation

The phase equilibria of the Y-Fe-B ternary system were investigated using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). Six ternary intermetallic compounds were identified through SEM-EDS analysis and XRD Rietveld refinements: Y₂Fe₁₄B (Nd₂Fe₁₄B-type structure and space group P4₂/mnm), YFe₄B₄ (Nd_1+ϵFe₄B₄-type structure and space group Pccn), YFe₂B₂ (CeAl₂Ga₂-type structure and space group I4/mmm), YFeB₄ (YCrB₄-type structure and space group Pbam), Y₅Fe₂B₆ (Pr₅Co₂B₆-type structure and space group R-3m) and Y₃FeB₇ (Y₃ReB₇-type structure and space group Cmcm). The solidification microstructure, phase compositions and phase transitions of Y_xFe_94-xB₆ and Y_11.7Fe_88.3-xB_x as-cast alloys were examined using SEM-EDS and differential scanning calorimetry (DSC). Furthermore, by integrating the previous calculations of the Y-Fe and Fe-B binary systems with the results determined in this study and reported in the literature, thermodynamic calculation of the Y-Fe-B ternary system was conducted by means of the CALPHAD method, based on the present optimization of the Y-B binary system. The calculated phase diagrams and thermodynamic properties of the Y-B binary system are in good agreement with the reported results, while the calculated vertical and isothermal sections of the Y-Fe-B ternary system are consistent with the experimental data. Finally, the available thermodynamic parameters for the Y-Fe-B ternary system were obtained, providing a robust foundation to develop a thermodynamic database of magnetic RE-Fe-B-based alloys.