Grain boundary restructuring of multi-main-phase Nd-Ce-Fe-B sintered magnets with Nd hydrides

Ma, Tianyu; Yan, Mi; Wu, Kaiyun; Wu, Bo; Liu, Xiaolian; Wang, Xuejiao; Qian, Zhi‐Gang; Wu, Chen; Xia, Weixing

doi:10.1016/j.actamat.2017.09.045

Cited by 104 publications

(33 citation statements)

References 45 publications

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“…The higher the concentration of elements, the greater the diffusion coefficient and diffusion tendency. At the same temperature, the diffusion activation energy of the melted RE-rich phase was much lower than that of the solid phase [23]. Therefore, the RE-rich phase also showed a larger diffusion coefficient than the main phase.…”

Section: Resultsmentioning

confidence: 99%

Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process

Zhong

Yang

et al. 2019

Materials

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The diffusion of Tb in sintered Nd-Fe-B magnets by the grain boundary diffusion process can significantly enhance coercivity. However, due to the influence of microstructures at different depths, the coercivity increment and temperature stability gradually decreases with the increase of diffusion depth, and exhibit good corrosion resistance at a sub-surface layer (300–1000 μm). According to the Electron Probe Micro-analyzer (EPMA) test results and the diffusion mechanism, the grain boundary and intragranular diffusion behavior under different Tb concentration gradients were analyzed, and the diffusion was divided into three stages. The first stage is located on the surface of the magnet, which formed a thick core-shell structure and a large number of RE-rich phases. The second stage is located in the sub-surface layer, forming a uniform and continuous RE-rich phase and thin core-shell structure. The third stage is located deeper in the magnet, and the Tb enrichment only existed at the triangular grain boundary.

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Section: Resultsmentioning

confidence: 99%

Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process

Zhong

Yang

et al. 2019

Materials

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“…Meanwhile, the high-abundant and cheap rare earth metals La, Ce, and Y were not used effectively in the production of Nd-Fe-B magnets. Therefore, the integrated utilization of rare earth metals in Nd-Fe-B magnets is a promising way to achieve the sustainable development of Nd-Fe-B magnets [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. However, the magnetic properties of Nd-Fe-B magnets with La, Ce, and Y have deteriorated unavoidably through the traditional fabrication technology because intrinsic magnetic properties of La 2 Fe 14 B, Ce 2 Fe 14 B, and Y 2 Fe 14 B phases are inferior to those of Nd 2 Fe 14 B, Dy 2 Fe 14 B, and Tb 2 Fe 14 B phases [ 35 ].…”

Section: Introductionmentioning

confidence: 99%

Phase Formation, Microstructure, and Magnetic Properties of Nd14.5Fe79.3B6.2 Melt-Spun Ribbons with Different Ce and Y Substitutions

Dai

et al. 2021

Materials

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Phase formation and microstructure of (Nd1-2xCexYx)14.5Fe79.3B6.2 (x = 0.05, 0.10, 0.15, 0.20, 0.25) alloys were studied experimentally. The results reveal that (Nd1-2xCexYx)14.5Fe79.3B6.2 annealed alloys show (NdCeY)2Fe14B phase with the tetragonal Nd2Fe14B-typed structure (space group P42/mnm) and rich-RE (α-Nd) phase, while (Nd1-2xCexYx)14.5Fe79.3B6.2 ribbons prepared by melt-spun technology are composed of (NdCeY)2Fe14B phase, α-Nd phase and α-Fe phase, except for the ribbon with x = 0.25, which consists of additional CeFe2 phase. On the other hand, magnetic properties of (Nd1-2xCexYx)14.5Fe79.3B6.2 melt-spun ribbons were measured by a vibrating sample magnetometer (VSM). The measured results show that the remanence (Br) and the coercivity (Hcj) of the melt-spun ribbons decrease with the increase of Ce and Y substitutions, while the maximum magnetic energy product ((BH)max) of the ribbons decreases and then increases. The tendency of magnetic properties of the ribbons could result from the co-substitution of Ce and Y for Nd in Nd2Fe14B phase and different phase constitutions. It was found that the Hcj of the ribbon with x = 0.20 is relatively high to be 9.01 kOe, while the (BH)max of the ribbon with x = 0.25 still reaches to be 9.06 MGOe. It suggests that magnetic properties of Nd-Fe-B ribbons with Ce and Y co-substitution could be tunable through alloy composition and phase formation to fabricate novel Nd-Fe-B magnets with low costs and high performance.

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“…The H cj of rare-earth permanent magnets is extremely sensitive to the microstructure in particular the grain size, grain alignment, and grain boundary (GB) configuration: (1) H cj changes with the variation of grain size and keeps at a high level for nanostructured magnets [2][3][4]; (2) H cj can be enlarged significantly by the alignment of the hard magnetic grains [5][6][7] and the formation of an adequate GB configuration [8][9]. Usually, nanostructured magnets are obtained through a rapid solidification process, and optimized GB configuration is achieved by conventional furnace an-nealing such as composition design, post-annealing, and/ or GB diffusion methods [10][11][12][13][14], which all have a low heating rate below 10 K s −1 . Inevitably, this low heating rate induces the grain growth and coarsening, resulting in a detrimental effect on permanent magnet performance [15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

A novel strategy for the fabrication of high-performance nanostructured Ce-Fe-B magnetic materials via electron-beam exposure

et al. 2021

Self Cite

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Ce 2 Fe 14 B compound has a great potential to serve as a novel permanent magnet alternative thanks to the abundant and inexpensive rare-earth element (cerium), while its low magnetocrystalline anisotropy and energy product severely restrict its applications. In this work, a novel strategy combining melt-spinning and electron-beam exposure (EBE) aiming for fabricating high-performance Ce-Fe-B magnetic materials is reported to solve the above-mentioned problem. Remarkably, this strategy facilitates developing a suitable grain boundary configuration without using any additional heavy rare-earth element. Under the optimal EBE condition, the maximum energy product ((BH) max ) of pure Ce-Fe-B alloy is 6.5 MGOe, about four times higher than that obtained after conventional rapid thermal processing method for the same precursor. The enhanced intergranular magnetostatic coupling effect in the EBE sample is validated by mapping the first-order-reversal-curve (FORC) diagrams. The in-situ observation of magnetic domain wall motion for Ce-Fe-B alloy using Lorentz transmission electron microscopy reveals that the boundary layers are very effective in pinning the motion of domain walls, leading to the increased coercivity under EBE, and this pinning effect is further verified by micromagnetic simulations. Our results suggest that CeFeB materials using EBE could be a promising candidate after further processing, which could fill the performance "gap" between hexaferrite and Nd-Fe-B-based magnets.

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Grain boundary restructuring of multi-main-phase Nd-Ce-Fe-B sintered magnets with Nd hydrides

Cited by 104 publications

References 45 publications

Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process

Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process

Phase Formation, Microstructure, and Magnetic Properties of Nd14.5Fe79.3B6.2 Melt-Spun Ribbons with Different Ce and Y Substitutions

A novel strategy for the fabrication of high-performance nanostructured Ce-Fe-B magnetic materials via electron-beam exposure

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