Microstructure and improved properties of sintered Nd-Fe-B magnets by grain boundary diffusion of non-rare earth

[Display omitted] •Magnetron sputtering was used to fabricate Al films.•High coercivity and excellent corrosion resistance were obtained.•A weak ferromagnetic phase within intergranular phase was investigated. Al film, which was coated in sintered Nd-Fe-B magnets prepared by magnetron sputtering, wa...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2019-04, Vol.476, p.134-141
Main Authors: Chen, W., Huang, Y.L., Luo, J.M., Hou, Y.H., Ge, X.J., Guan, Y.W., Liu, Z.W., Zhong, Z.C., Wang, G.P.
Format: Article
Language:English
Subjects:
Al film
Coercivity
Corrosion resistance
Diffusion coating
Diffusion effects
Electrochemical potential
Ferromagnetic phases
Ferromagnetism
Ferrous alloys
Grain boundaries
Grain boundary diffusion
Intergranular corrosion
Iron
Magnetic materials
Magnetic properties
Magnetron sputtering
Magnets
Microstructure
Neodymium
RE-rich phase
Sintering
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Summary:[Display omitted] •Magnetron sputtering was used to fabricate Al films.•High coercivity and excellent corrosion resistance were obtained.•A weak ferromagnetic phase within intergranular phase was investigated. Al film, which was coated in sintered Nd-Fe-B magnets prepared by magnetron sputtering, was employed for grain boundary diffusion source. Effects of the grain boundary diffusion processes (GBDP) on the microstructure evolution and properties were investigated in detail. Through grain boundary diffusion processes, the highest coercivity of 1184 kA/m and maximum energy product of 238 kJ/m3 could be obtained, increasing by 21.8% and 3.9%, respectively, compared with the initial magnet. Meanwhile, our results showed that fine, uniform and continuous intergranular phase induced by Al diffusion, was the main reason for properties improvement, while a weak ferromagnetic phase and the vague interface between main phase and RE-rich phase should be responsible to the deterioration of coercivity when the diffused temperature exceed 600 °C. Besides, the corrosion resistance of Al-diffused magnets was also greatly improved, owing to the fact that the Al element could promote the electrochemical potential of RE-rich phase and the more thin, continuous intergranular phase would also narrow the corrosion channel.
ISSN:0304-8853
1873-4766
DOI:10.1016/j.jmmm.2018.12.048