Effects Of Spark Plasma Sintering And Additives In The Grain Boundary On The Microstructure And Magnetic Properties Of Sintered NdFeB

The excellent magnetic properties make Nd-Fe-B permanent magnets of significant and growing commercial importance for many applications. Therefore, the researches on properties and preparation technologies for this material have been receiving considerable attention over the past two decades. To explore the new application field of Nd-Fe-B, the magnets was made by the new technology Spark Plasma Sintering. Effects of Oxides and Nitrides added in the Grain Boundary on the microstructure and Magnetic Properties of Sintered NdFeB were also studied in this paper. A series of equipments such as scanning electronic microscope(SEM), transmission electronic microscope(TEM) and other metrology instruments were used to investigate the effect of preparation technologies on the microstructure and properties of these magnets systematically.New technology Spark Plasma Sintering was tried to prepare the magnets with high magnetic properties and high dimensional precision. The effects of SPS sintering temperature and tempering technology on the microstructure and Magnetic Properties were studied. It was found that proper sintering temperature and tempering technology optimized the microstructure of the magnets, increased the magnetic properties greatly. Otherwise, tempering technology changed the Nd-rich phase in the triangle grain boundary from dhcp structure to fcc structure by the observation of TEM.Oxides and nitrides were added in the grain boundary during the ball milling in order to increase the magnetic properties and corrosion resistance. Effects of different content on the microstructure, magnetic properties and corrosion resistance were studied. It was found that both romance and maximum energy product were increased at minor additives. Furthermore, corrosion resistance of magnets was improved when Si3N4 was added.