Reduction of the mechanical anisotropy in hot-deformed Nd-Fe-B magnets by the construction of heterogeneous structure

Abstract

Conventional hot-deformed Nd-Fe-B magnets exhibit significant mechanical anisotropy in the two directions perpendicular and parallel to c-axis, resulting in a complicated machining process. In this work, hydrogenation-disproportionation-desorption-recombination (HDDR) powders were added to reduce the mechanical anisotropy of hot-deformed magnets. The effects of the addition of HDDR powders on the compressive strength of hot-deformed magnets and their corresponding microstructures have been investigated. The mechanical anisotropy was maximally decreased by 68 % at 20 wt. % addition. Microstructure observation indicated that a heterogeneous structure containing two kinds of grains with different morphology was formed after the addition of HDDR powders. Further analyses revealed that the reduction of mechanical anisotropy was mainly attributed to the change of the shape anisotropy of grains and the disruption of the regular stacking structure of the melt-spun ribbons. This work provides a new insight for the preparation of high performance hot-deformed Nd-Fe-B magnet with outstanding comprehensive service capability.