Microstructure and magnetic properties of anisotropic Nd-Fe-B magnets produced by spark plasma sintering technique

摘要

Bulk anisotropic Nd-Fe-B magnets were synthesized by hot pressing and subsequent hot deforming melt-spun ribbons using spark plasma sintering (SPS) technique. Influences of grains morphology and Nd-rich intergranular phase distribution on magnetic properties of both hot pressing and hot deforming magnets were investigated. Compared with starting ribbons, randomly oriented Nd_2Fe_(14)B grains in hot pressing magnets increased their average size from 40 to 100 nm, which led to a slightly reduction of coercive force of the magnets. After hot deformation, the interior of the magnets consisted of well-aligned platelet shaped Nd_2Fe_(14)B grains with 80 nm in thickness and 200-500 nm in length. On the other hand, most Nd-rich phase in the magnets redistributed from grain boundaries to triple junctions of the Nd_2Fe_(14)B grains. The resultant magnets exhibited a remanence (Br) of 1.34 T, coercive force (Hci) of 512kA/m, and maximum energy product ((BH)_(max)) of 280kJ/m~3.