Comparisons of the Microstructure and Magnetic Properties of Anisotropic NdFeB Magnets Prepared by Hot Pressing and Spark Plasma Sintering

NdFeB hot-pressed and hot-deformed magnets were prepared by hot-pressed (HP) sintering and spark plasma sintering (SPS). The effects of sintering mechanisms of SPS and HP on the microstructure of hot deformation magnets were studied. The temperature of the mold surface is much higher than that of the sample in the cavity in HP, but lower than that of the sample in SPS. The Nd-rich phase is uniformly distributed and the grain size is smaller in the hot-deformed magnets prepared by HP, while the Nd-rich phase is excessively enriched and the grain size in the liquid-enriched region is abnormal in the hot-deformed magnets prepared by SPS. The comprehensive magnetic properties of hot deformed magnets prepared by SPS are significantly lower than those prepared by HP.