Isotropic and Anisotropic Nanocrystalline NdFeB-Based Magnets Prepared by Spark Plasma Sintering and Hot Deformation

Liu, Zhongwu; Huang, Yanjiang; Huang, Hai-Jun; Zhong, Xichun; Yu, Hong; Zeng, D.C.

doi:10.4028/www.scientific.net/kem.510-511.307

Cited by 9 publications

(2 citation statements)

References 16 publications

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“…The internal part of the particles is built of the fine grain zone. This finding clarifies, generally observed fact, that sintering of coarser powders provides higher coercivity [6].…”

Section: Introductionsupporting

confidence: 88%

Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

Kaszuwara¹,

Leonowicz²,

Michalski³

et al. 2013

EPJ Web of Conferences

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Abstract. In this study the SPS method was applied for low RE content (8,5% at.) and high RE content (13,5 % at.) MQ powders. The powders were sintered in a wide range of temperature, for 5 min., under pressure of 35 MPa. The low RE content grade, densified reluctantly and gained the density close to the theoretical value only for 850 o C. The coercivity decreased gradually with increasing sintering temperature. On the other hand, the densification of the higher RE content grade powder occurred much easier and the coercivity, close to the theoretical value, was achieved already at 650 o C. The coercivity of this material also decreased with increasing sintering temperature. Microstructural studies revealed that the SPS sintering process leads to partial decomposition of the Nd 2 Fe 14 B phase. The proportion of the RE-rich and iron phases increases parallel to the increasing sintering temperature. On the basis of the current results one can conclude that fabrication of high density MQ powders based magnets by the SPS method is possible, however the powders having higher RE content should be used for this purpose and the sintering temperature as low as possible, related to density, should be kept.

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“…The internal part of the particles is built of the fine grain zone. This finding clarifies, generally observed fact, that sintering of coarser powders provides higher coercivity [6].…”

Section: Introductionsupporting

confidence: 88%

Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

Kaszuwara¹,

Leonowicz²,

Michalski³

et al. 2013

EPJ Web of Conferences

View full text Add to dashboard Cite

show abstract

“…Concurrently Gopalan et al [17] were able to increase the remanence after hot deformation from 1.07 T to 1.35 T in the precursor HDDR powder of composition Nd 14.1 Fe 78.2 Co 1.0 B 6.1 Cu 0.1 Al 0.5 . Likewise, Li et al [18] obtained B r = 1.09 T and BH max = 114 kJ/m 3 after HDDR powder hot deformation through SPS, but the H Ci was only 384 kA/m, due to grain shape factor and interlinked with the abnormal grain growth of Nd 2 Fe 14 B crystallites. The hot deformation temperatures were identified by Li et al [19], achieving 69% height reduction, B r = 1.22 T and yet again low H Ci = 181 kA/m and BH max = 121 kJ/m 3 only.…”

Section: Introductionmentioning

confidence: 92%

Spark Plasma Sintering as an Effective Texturing Tool for Reprocessing Recycled HDDR Nd-Fe-B Magnets with Lossless Coercivity

Ikram

Awais

Sheridan

et al. 2020

Metals

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The low-pressure hot-deformation methodology was applied to reprocess the nanocrystalline hydrogenation–disproportionation–desorption–recombination (HDDR) Nd-Fe-B powders from end-of-life (EOL) permanent magnets’ waste to determine the mechanism of texture development and the resultant improvement in remanence (and BHmax) in the recycled material. Both the hot-pressed and hot-deformed magnets produced via spark plasma sintering (SPS) were compared in terms of their magnetic properties with respect to forging pressures. Also, a comparison was established with the microstructure to cite the effectiveness of texture development at low deformation rates and pressures which is pivotal for retaining high coercivity. The hot-pressed magnets maintain the high coercivity (better than 100%) of the original recycled powder due to the control of SPS conditions. The hot deformation pressure was varied from 100–150 MPa at 750 °C processing temperature to identify the optimal texture development in the sintered HDDR Nd-Fe-B magnets. The effect of post-hot-deformation thermal treatment was also investigated, which helped in boosting the overall magnetic properties and better than the recycled feedstock. This low-pressure hot deformation process improved the remanence of the hot-pressed magnet by 11% over the starting recycled powder. The Mr/MS ratio which was 0.5 for the hot-pressed magnets increased to 0.64 for the magnets hot-deformed at 150 MPa. Also, a 55% reduction in height of the sample was achieved with the c-axis texture, indicating approximately 23% higher remanence over the isotropic hot-pressed magnets. After hot deformation, the intrinsic coercivity (HCi) of 960 kA/m and the remanence (Br) value of 1.01 T at 150 MPa is indicative that the controlled SPS reprocessing technique can prevent microstructure related losses in the magnetic properties of the recycled materials. This route also suggests that the scrap Nd-Fe-B magnets can be treated with recoverable magnetic properties subsequently via HDDR technique and controlled hot deformation with a follow-up annealing.

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Microstructural and Magnetic Properties of Nanocrystalline Nd-Fe-B Rare Earth Magnet Prepared by Spark Plasma Sintering Technique

Singh,

Diraviam,

et al. 2024

J Supercond Nov Magn

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Isotropic and Anisotropic Nanocrystalline NdFeB-Based Magnets Prepared by Spark Plasma Sintering and Hot Deformation

Cited by 9 publications

References 16 publications

Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

Spark Plasma Sintering as an Effective Texturing Tool for Reprocessing Recycled HDDR Nd-Fe-B Magnets with Lossless Coercivity

Microstructural and Magnetic Properties of Nanocrystalline Nd-Fe-B Rare Earth Magnet Prepared by Spark Plasma Sintering Technique

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