Microstructure and magnetic properties of hot-deformed anisotropic Nd-Fe-B magnets prepared from amorphous precursors with different crystallization proportions

Anisotropic magnets were obtained by hot deformation with the partial crystallized precursor prepared via spark-plasma sintering (SPS). Amorphous powders with the nominal composition of Nd28.72FebalCo5.66Ga0.59B0.92 (wt%) were used as the starting material. The results show that the amorphous powders would suffer varying degrees of crystallization even below the crystallization point during the SPS process under high pressure. And the pre-crystallized grains in precursors have great impacts on the microstructure and magnetic properties of the hot-deformed magnets. The final obtained anisotropic magnets exhibit homogeneous microstructure consisting of well-aligned and platelet-shaped Nd2Fe14B grains without abnormal growth. It can be found that a reasonable proportion of pre-crystallized gains could promote the preferential orientation in the magnet, leading to the achievement of optimal magnetic properties among the magnets with identical composition and best magnetic performance is achieved in the magnet hot deformed from the 490 A degrees C high-pressure hot-pressed precursor.