Intermediate hydrogenation phase in the hydrogenation–disproportionation–desorption–recombination process of Nd 2Fe 14B-based anisotropic magnets

Abstract

To understand the disproportionation and anisotropy-inducing mechanism of the hydrogenation–disproportionation–desorption–recombination process of Nd 2Fe 14B-based anisotropic magnets, the disproportionated structure of Nd 13.0Fe 67.9Co 11.0B 7.0Ga 1.0Zr 0.1 alloys has been investigated via transmission electron microscopy. An intermediate hydrogenation phase of the tetragonal Fe 3B (t-Fe 3B) has been revealed to appear in the early stage of disproportionation. The t-Fe 3B possesses lattice coherency and an associated “one-to-one” orientation relationship with the parent Nd 2Fe 14B phase. Within the t-Fe 3B grain, fine Nd 2Fe 14B particles exist along with NdH 2 particles. The diameter of the Nd 2Fe 14B particles is around 50 nm, and they have close orientation to that of original Nd 2Fe 14B. An anisotropy-mediating disproportionation scheme with the intermediate hydrogenation phase is proposed.