LAUSR

Abstract The phase equilibrium relationships of the Ho-Fe-B system at 800 °C were investigated using diffusion couples and aided by the application of equilibrium alloys. This is critical for the design of high performance multiphase rare earth permanent magnetic materials. The experimental data were obtained from diffusion couples using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA),and the isothermal section of the Ho-Fe-B system at 800 °C was established. The X-ray diffraction was used to analyze eight essential equilibrium alloys at 800 °C to further determine the reliability of the diffusion couple determination phase diagram. Experimental results clearly show the applicability of the diffusion couples’ approach in determining such complex phase diagrams as Ho-Fe-B. The isothermal section at 800 °C was constructed from the results obtained from diffusion couples which contains 17 three-phase equilibrium regions and three stable ternary compounds Ho2Fe14, Ho5Fe17B17 and HoFeB3.