Effect of Copper and Titanium Addition on Microstructures and Magnetic Properties of Sintered NdFeB Magnets

The alloying elements Cu/Ti were added into the intergranular regions of sintered NdFeB magnets, and their effects on microstructure and magnetic properties were investigated. The results show that small amount of Cu/Ti additives can enhance the coercivity greatly and have little effect on the remanence of the magnets, while Ti content is less than 1 2%. The improvement of the coercivity can be attributed to the segregation of Cu and Ti on the surface of main phase, which inhibits the growth of main phase grain during the sintering. At the same time, the segregation of Cu and Ti can also prevent the magnetic coupling of Nd 2Fe 14 B grains to a certain degree and impede effectively the propagation of reversed domain walls through the magnetic phase grains. With the Ti content increasing above 1 2%, a strip Ti rich phase appears in the intergranular region, resulting in the dramatic reduction of the remanence of Nd Fe B magnets. Compared with the single alloying method, the combined alloying of intergranular region is more efficient to modify the properties of NdFeB magnets.