Phase Equilibria of the Nd-Fe-B Ternary System

Abstract

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 REl.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.