USE OF HYDROGEN-CONTAINING REM-BASED ADDITIONS IN DESIGNING RE-Fe-B MAGNETIC MATERIALS

Abstract

The focusing of new technologies on the formation of inhomogeneous distributions of heavy rare-earth metals (REMs) in hard magnetic Nd-Fe-B materials is of scientific importance for increasing their functional properties, along with preserving existing sources of heavy REMs. The manufacturing process for these materials includes strip-casting, hydrogen decrepitation, and treatments in a hydrogen atmosphere, as well as high-energy milling combined with mechanical alloying of multicomponent powder mixtures. The role of alloying REMs and their alloys with transition metals on the formation of phase composition, microstructure, fine structure of grains, and the hysteretic properties of hard magnetic (RR')2Fe14B-based materials were investigated. These addition were introduced in the form of hydrides or hydrogenated alloys (TbHx, DyHx, ScHx, Tb3(Co,Cu), Dy3(Co,Cu)) to initial Nd(Pr)-Fe-B-based powder mixtures in the course of their mechanical activation. The new knowledge about the formation of the structured state of (RR')2Fe14B-phase grains, namely, the formation of compositional inhomogeneities of heavy REMs within grains was obtained. The core-shell grain structure so formed and the nonuniformity of the main hard magnetic phase lead to increases in the structure-sensitive magnetic parameters and to their higher stability during low-temperature annealing. The powder-blending manufacturing process allows us to prepare magnets with a wide range of hysteretic characteristics using unified initial Nd-Fe-B strip-casting alloys.