Effect of Different Grain Boundary Diffusion Alloys on Magnetic Properties of Dy-Free Sintered NdFeB Magnet

Dy-free sintered magnets were fabricated by blending Neo powder with different grain boundary diffusion (GBD) alloy powders. Cu, CeAl, and CeAlCu have a negative effect on H(cj )of magnets, while PrAlCu and AlCuGa have a positive effect. The PrAlCu-added magnet achieves the best magnetic properties among all magnets with the additions of different diffusion alloys. With increasing PrAlCu from 0-10 wt.%, H-cj of the magnets gradually increases from the original 14.5-19.2 kOe. The magnet with 7.5 wt.% PrAlCu obtains an Hcj of 18 kOe and (BH)(max) of 39.1 MGOe. It is found that Pr and Cu in PrAlCu alloy are mainly distributed at grain boundary and triple junctions (TJs), leading to a reduced coupling among grains, thus an enhanced H-cj. The grain boundary engineering by adding an appropriate alloy is an effective method to improve H-cj of Dy-free NdFeB magnets.