Microstructural modification of grain boundary area in WS2/Al co-doped Nd-Fe-B sintered magnet

We investigated the effect of microstructural modification of grain boundary area and WS2 powder size on the magnetic properties of WS2/Al-doped Nd-Fe-B sintered magnet. Grain growth inhibition (7.6 → 6.4 μm) in optimally doped magnet with Dy-rich core-shell microstructure was effectively improved t...

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Bibliographic Details
Published in:Intermetallics 2018-01, Vol.92, p.93-100
Main Authors: Bae, Kyoung-Hoon, Lee, Seong-Rae, Kim, Hyo-Jun, Lee, Min-Woo, Jang, Tae-Suk
Format: Article
Language:English
Subjects:
Coercivity
Core-shell microstructure
Effects
Ferrous alloys
Grain boundaries
Grain growth
Grain growth inhibition
Iron
Magnetic materials
Magnetic properties
Magnets
Microstructure
Nd-Fe-B sintered magnet
Neodymium
Precipitates
Sintering (powder metallurgy)
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Summary:We investigated the effect of microstructural modification of grain boundary area and WS2 powder size on the magnetic properties of WS2/Al-doped Nd-Fe-B sintered magnet. Grain growth inhibition (7.6 → 6.4 μm) in optimally doped magnet with Dy-rich core-shell microstructure was effectively improved the magnetic properties compared with only doped magnet. In the case of only doped magnet, the lattice misfit between the (002) WFeB precipitates and (110) Nd2Fe14B interfaces was about 9.9%, which caused the strong strain fields at the grain boundaries. However, the doped magnet with Dy-rich core-shell exhibited a decreased lattice misfit (9.9 → 3.4%) owing to the formation of the high anisotropic Dy-rich (Nd,Dy)2Fe14B phase around the GB area, thus suppressing reverse-domain nucleation at the grain boundaries. As a result, the coercivity increments in the optimally doped magnets with Dy-rich core-shell (6.5%) was larger than that of only doped magnets (3.9%) compared with each corresponding undoped magnet. When the particle size of WS2-doped powders was reduced (∼2.0 → ∼0.6 μm), the coercivity further increased owing to the improved inhibition of grain growth although the doping content of WS2 was reduced from 0.6 to 0.4 wt%. [Display omitted] •The lattice misfit between the WFeB and Nd2Fe14B in the only doped magnet was reduced due to the Dy-rich core-shell.•The reverse-domain nucleation at the WFeB/Nd2Fe14B interface was effectively suppressed.•The coercivity increments in the doped magnet with Dy-rich core-shell was larger than that of only doped magnet.•The average grain size and distribution were optimized as the WS2 powder size was reduced (2.0 → 0.6 µm).
ISSN:0966-9795
1879-0216
DOI:10.1016/j.intermet.2017.09.022