Phase Equilibria of the Nd-Fe-B Ternary System

Nd-Fe-B-based alloys as sintered Nd₂Fe₁₄B-typed permanent magnets have been studied extensively due to their excellent magnetic properties. In this work, the experimental information on the corresponding phase equilibria of the Nd-Fe-B ternary system in the published literature is reviewed first. The key Nd-Fe-B alloys annealed at 873 and 1073 K were then investigated experimentally to determine the phase equilibria of the system using x-ray diffraction technique and scanning electron microscope (SEM) with energy dispersive spectrometry (EDS). The ternary intermetallic compound, Nd₂Fe₁₄B with space group P4₂/mnm as Nd₂Fe₁₄B structure type, NdFe₄B₄ with space group Pccn as RE_l.11Fe₄B₄ structure type and Nd₅Fe₂B₆ with space group R \( \overline{3} \) m as Pr₅Co₂B₆ structure type were confirmed at 873 and 1073 K. The binary intermetallic compound Nd₅Fe₁₇ is stable at 873 K, while it was not found at 1073 K. The phase equilibria of the Nd-Fe-B ternary system consists of 14 single-phase regions, 28 two-phase regions and 16 three-phase regions at 873 K, while there are 8 single-phase regions, 14 two-phase regions and 7 three-phase regions at 1073 K except for the B-rich part.