Effects of excessive grain growth on the magnetic and mechanical properties of hot-deformed NdFeB magnets

Lin, Min; Wang, H.J.; Yi, Pengpeng; Yan, Aru

doi:10.1016/j.jmmm.2010.02.023

Cited by 44 publications

(10 citation statements)

References 13 publications

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“…9(a) and 9(b). Both of these regions grow rapidly with the increase of the deformation temperature [16] and degree of deformation. [21] The two kinds of grains are disadvantageous with respect to magnetic properties.…”

Section: Inhomogeneity Of Microstructure In Hd Magnetmentioning

confidence: 99%

“…Based on the preceding analysis, the deformation temperature was optimized to be in the range 820-840 • C. The remanence, coercivity, and maximum energy product of the HD magnet deformed at 840 • C are 13.8 kG, 15.8 kOe, and 46.5 MGOe, respectively. Lin et al [16] reported that abnormal grain growth and Nd-rich phase extrusion occur when the HD temperature is higher than 850 • C, which leads to a reduction of the density and remanence. Zhao et al [17] reported that the effective anisotropy can be obtained at the HD temperature of 600-900 • C. In their work, it was shown that a suitable HD temperature was about 800 • C. It should be noted that the suitable HD temperature varies based on the different heating methods.…”

Section: Hd Temperaturementioning

confidence: 99%

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Rare earth permanent magnets prepared by hot deformation process

et al. 2018

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Hot deformation is one of the primary methods for fabricating anisotropic rare earth permanent magnets. Firstly, rapidly quenched powder flakes with a nanocrystal structure are condensed into fully dense isotropic precursors using the hot-pressing process. The prepared isotropic precursors are then hot-deformed to produce high-anisotropy uniaxial bulk rare earth permanent magnets and a highly textured structure is produced via this process. The resulting magnets possess many advantages such as near-net-shape, outstanding corrosion resistance, and ultrafine-grain structure. The influence of the preparation parameters utilized in the hot-pressing and deformation processes on the magnetic properties and microstructure of the permanent magnets are systemically summarized in this report. As a near-net-shape technique, the hot deformation process has notable advantages with regard to the production of irregular shapes, especially for radially oriented ringshaped magnets with high length-diameter ratios or thin walls. The difficulties associated with the fabrication of crack-free, homogeneous, and non-decentered ring-shaped magnets are substantially resolved through an emphasis on mold design, adjustment of deformation parameters, and application of theoretical simulation. Considering the characteristics of hotdeformed magnets which include grain shape and size, anisotropic distribution of intergranular phases, etc., investigation and improvement of the mechanical and electric properties, in addition to thermal stability, with the objective of improving the application of hot-deformed magnets or ring-shaped magnets, is of practical significance.

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Section: Inhomogeneity Of Microstructure In Hd Magnetmentioning

confidence: 99%

Section: Hd Temperaturementioning

confidence: 99%

Rare earth permanent magnets prepared by hot deformation process

et al. 2018

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“…[ 8 ] The anisotropy relies on the stress‐induced grain growth and the lubrication of the melted grain boundary RE‐rich phase, which causes the sliding or rotation of the grains. [ 9 ] Therefore, the magnetic properties of hot‐deformed magnets are closely related to their microstructure. The crystal orientation and grain boundary phase distribution are particularly important.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Anisotropic Nanocrystalline NdFeB Magnets from Amorphous Powders by One‐Step Hot Deformation

Huang

Liao

et al. 2022

Adv Eng Mater

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The preparation of nanocrystalline anisotropic NdFeB permanent magnets generally includes two steps, hot pressing (HP) and hot deformation (HD). Herein, one‐step HD process is proposed to fabricate NdFeB magnets using amorphous powders. The effects of deformation ratio on the microstructure, magnetic properties, and corrosion resistance are investigated. Compared to traditional HP and HD process, one‐step HD can significantly reduce the volume fraction of coarse‐grain zone in the magnet. The increase of deformation ratio can promote the formation of the textured platelet‐shaped grains and uniform grain boundary phase. The magnetic properties, temperature stability, and corrosion resistance of the magnets increase with increasing deformation ratio until 80%. The best magnetic properties with intrinsic coercivity Hcj = 930 kA m−1, remanence Jr = 1.17 T, and maximum energy product (BH)max = 263 kJ m−3 have been achieved for the magnet prepared by one‐step HD, which are comparable to those obtained by conventional HP/HD. In addition, different Co element segregations are observed in the magnets with different deformation ratios, which have important effects on the Curie temperature and thermal stability of the magnets. The results suggest that, by replacing HP/HD process and using amorphous powder, one‐step HD can simplify the process while maintaining good properties.

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“…Therefore, material flow at the axially middle cross-section is easier than that at end surfaces. As a ternary alloy, Nd-Fe-B could be deformed from a Manuscript thin cylinder into a fat one at 650 C-850 C [16], [17]. The unevenness of material flow in a Nd-Fe-B magnet during this deformation was merely mentioned in [18].…”

Section: Introductionmentioning

confidence: 99%

Origins of Radial and Axial Inhomogeneity of Magnetic Performance in Cylindrical Nd-Fe-B Magnet Prepared by Hot Deformation

et al. 2014

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Cylindrical Nd-Fe-B magnets with different height reductions were prepared by hot deformation method. The inhomogeneity of the magnetic performance along the radial direction was revealed with a closed circuit B-H apparatus while that along the axial direction was shown with a vibrating sample magnetometer. The microstructure examined with scanning electron microscopy suggests that orientation variation and grain coarsening of Nd Fe B platelets cooperate to result in the deterioration of remanence along radial direction from center to edge. X-ray diffractometry was carried out over the end surfaces and axially across the middle cross-section of the cylindrical magnet, showing the important role of texture in determination of remanence along the axial direction. Further investigations on an intermediate hot-deformed magnets reveal the unevenness of deformation degree in the axial direction during hot deformation, which accounts for the axial variation of texture and consequent remanence.

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Effects of excessive grain growth on the magnetic and mechanical properties of hot-deformed NdFeB magnets

Cited by 44 publications

References 13 publications

Rare earth permanent magnets prepared by hot deformation process

Rare earth permanent magnets prepared by hot deformation process

Preparation of Anisotropic Nanocrystalline NdFeB Magnets from Amorphous Powders by One‐Step Hot Deformation

Origins of Radial and Axial Inhomogeneity of Magnetic Performance in Cylindrical Nd-Fe-B Magnet Prepared by Hot Deformation

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