Magnetic Properties of Hot Deformed and Boundary Diffused Nd-Fe-B Permanent Magnet

Nd-Fe-B is the third generation rare-earth permanent magnet, which exhibits much better magnetic properties than Sm-Co. It is widely used in industry and daily life, like DC motors, computer hardware, and motor vehicles, due to its excellent performance. In this paper, a Nd-Fe-B magnet with both hard magnetic Nd2Fe14B phase and soft magnetic α-Fe phase was produced by arc melting and then melt spinning in an overquenched state. The as-spun ribbons were annealed at different time and temperature to obtain the best magnetic properties. Spark plasma sintering (SPS) was then adopted to consolidate the as-spun ribbons, followed by hot deformation and grain boundary diffusion. Crystallographic alignment was successfully achieved after hot deformation, which increased the remanence. Coercivity was also increased by the grain boundary diffusion. The improvement of both remanence and coercivity raised the energy product, (BH)max, of the material to a high value. Dy was then introduced to the composition, which increased the original coercivity of the magnet, and resulted in a further improvement of the magnetic properties. The microstructure was characterized by X-ray diffraction and scanning electron microscopy, which confirm the crystallographic alignment of the magnet. Advisor: Jeffrey Shiel