Experimental Investigation of Phase Equilibria in the La-Fe-B System at 600 and 800 °C

Based on the highly efficient diffusion couple and equilibrated alloy methods, phase relations in La-Fe-B ternary system were experimentally investigated by scanning electron microscopy, electron probe microanalysis and electron backscatter diffraction techniques. Isothermal sections of the La-Fe-B system at both 600 and 800 °C were constructed. One ternary phase (LaFe 4 B 4 -τ 2 ) was detected at 600 °C and two ternary compounds (τ 2 and La 2 Fe 14 B-τ 1 ) were determined at 800 °C. Seven three-phase zones were found at 600 °C and ten three-phase regions were found at 800 °C. Liquid phase was found in the La-rich corner at 800 °C. The solid solubility of both binary and ternary compounds in the system is negligible. The present experimental results are important for the design of multi-main-phase Nd-La-Ce-Fe-B magnets.