Abstract:Bulk anisotropic Nd-Fe-B magnets were prepared from hydrogen-disproportionation-desorption-recombination (HDDR) powders via spark plasma sintering (SPS) and subsequent hot deformation. The influence of sintering temperature on the structure and magnetic properties of the spark plasma sintered Nd-Fe-B magnets were studied. The remanence B_r, intrinsic coercivity H_cj, and the maximum energy product (BH)_max, of sintered Nd-Fe-B magnets first increase and then decrease with the increase of sintering temperature, T_SPS, from 650 °C to 900 °C. The optimal magnetic properties can be obtained when T_SPS is 800 °C. The Nd-Fe-B magnet sinter treated at 800 °C was subjected to further hot deformation. Compared with the starting HDDR powders or the SPS treated magnets, the hot-deformed magnets present more obvious anisotropy and possess much better magnetic properties due to the good c-axis texture formed in the deformation process. The anisotropic magnet deformed at 800 °C with 50% compression ratio has a microstructure consisting of well aligned and platelet-shaped Nd₂Fe₁₄B grains without abnormal grain growth and exhibits excellent magnetic properties parallel to the pressing axis.

Key words: Nd-Fe-B magnet; hydrogen-disproportionation-desorption-recombination (HDDR); spark plasma sintering; hot deformation; magnetic property