Journal Article10.1109/tmag.2021.3136932
Microstructure Optimization and Magnetic Properties Enhancement of Hot Deformed Nd-Fe-B Magnets via Grain Boundary Diffusion and Secondary Hot Deformation
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TL;DR: In this article , hot deformation processes have an important influence on magnetic properties and microstructure, among which the deformation condition of 700 °C/0.5 h is the most favorable to obtain optimal magnetic properties.
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Abstract: Based on spark plasma sintered (SPS) Nd-Fe-B magnets with PrCu sintering aid, hot deformed (HD) magnets are prepared through hot deformation technique. After that, using PrCu as the diffusion source, grain boundary diffusion (GBD) is implemented on HD magnet. Eventually, GBD magnet is subjected to hot deformation to regulate the distribution of RE-rich phase and increase <inline-formula> <tex-math notation="LaTeX">$c$ </tex-math></inline-formula>-axis orientation, referred to as the secondary deformation (SD). The results show that hot deformation processes have an important influence on magnetic properties and microstructure, among which the deformation condition of 700 °C/0.5 h is the most favorable to obtain optimal magnetic properties. Through GBD, the coercivity, as high as 2117 kA/m, can be obtained, increasing by 7.5% comparing with that of the initial SPS sample. Moreover, it is found that the SD can effectively optimize the distribution of RE-rich phase, and improve <inline-formula> <tex-math notation="LaTeX">$c$ </tex-math></inline-formula>-axis orientation of grains. Eventually, a good balance between coercivity and remanence is achieved. In addition, both GBD and SD can increase the thermal stability of HD magnets.
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Citations
Coercivity enhancement of hot-deformed NdFeB magnets by in situ two-end-diffusion with R70Cu30 alloy powders (R = NdPr and Ce)
TL;DR: In situ two-end diffusion (TED) was proposed in this paper to reach coercivity enhancement with almost unchanged energy product for hot deformed (HD) NdFeB magnets.
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TL;DR: Considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed and their potential impact on energy efficiency is discussed.
Analysis of the magnetic hardening mechanism in RE-FeB permanent magnets
TL;DR: In this article, a detailed analysis of the temperature dependence of H c is given on the basis of the predictions of micromagnetic theories for pinning and nucleation mechanisms, and it is shown that the nucleation theory leads to a coherent interpretation of all relevant properties of Hc than the pinning theory if the effects of misaligned grains, local stray fields and reduced anisotropies in grain boundaries are taken into account.
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TL;DR: This study describes the first fabrication of a novel bimorphological anisotropic bulk nanocomposite using a multistep deformation approach, which outperforms, for the first time, the corresponding pure rare-earth magnet with 58% enhancement in energy product.
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