• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.381-388
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• 2000

By applying Current-applied Pressure-Assisted process, we could obtain full dense isotropic and anisotropic NdFeB magnets from rapidly quenched MQP-A powder. The Nd contents are found to play an important role during the CA-press and CA-deformation process. The (BH)$\sub$max/ of CA-pressed and CA-deformed magnets are 131 kJ/㎥(16.5 MGOe) and 352 kJ/㎥(44.2 MGOe), respectively. The texture of CA-deformed anisotropic NdFeB magnets with thickness reduction was investigated by pole figure, and the (006) texture was increase with the increase of thickness reduction. With the increment in thickness reduction from 50%, 60% to 80%, W$\sub$50/ decreases from 76$\^$$^{\circ}$/, 62.5$\^$$^{\circ}$/ to 17$\^$$^{\circ}$/, respectively.

• Journal of Magnetics
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• v.5 no.4
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• pp.130-134
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• 2000

Using the current-applied pressure-assisted (CAPk) process, we could obtain fully dense isotropic and anisotropic NdFeB magnets from rapidly quenched MQP-A powder. The Nd content is found to play an important role during the current applied (CA)-pressing and CA-deformation processes. The $(BH)_max$ of CA-pressed and CA-deformed magnets are 131 kJ/$m^3$ (16.5 MGOe) and 352 kJ/$m^3$(44.2 MGOe), respectively. The change in texture of CA-deformed anisotropic NdFeB magnets with thickness reduction was investigated by pole figures and the (006) texture was found to increase with greater thickness reductions. As the thickness reduction increases from 50% to 60% to 80%, $W_50$ (the average angle of the contour with 50% intensity) decreases from $76^\circ$to $62.5^\circ$to $17^\circ$.

• Journal of Magnetics
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• v.20 no.4
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• pp.336-341
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• 2015

MnBi alloys were fabricated by arc melting and annealing at 573 K. The heat treatment enhanced the content of the low-temperature phase (LTP) of MnBi up to 83 wt%. The Bi-excess assisted LTP MnBi alloys were used in the hybridization with the Nd-Fe-B commercial Magnequench ribbons to form the hybrid magnets (100-x)NdFeB/xMnBi, x = 20, 30, 40, 50, and 80 wt%. The as-milled powder mixtures of Nd-Fe-B and MnBi were aligned in a magnetic field of 18 kOe and warm-compacted to anisotropic and dense bulk magnets at 573 K by 2,000 psi for 10 min. The magnetic ordering of two hard phase components strengthened by the exchange coupling enhanced the Curie temperature ($T_c$) of the magnet in comparison to that of the powder mixture sample. The prepared hybrid magnets were highly anisotropic with the ratio $M_r/M_s$ > 0.8. The exchange coupling was high, and the coercivity $_iH_c$ of the magnets was ~11-13 kOe. The maximum value of the energy product $(BH)_{max}$ was 8.4 MGOe for the magnet with x = 30%. The preparation of MnBi alloys and hybrid magnets are discussed in details.

• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.250-255
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• 2001

Magnetic properties of the isotropic and anisotropic NdFeB magnets obtained by the Current-Applied Pressure-Assisted (CAPA) process from a melt-spun NdFeB powder were investigated using B-H loop analyser. The coercivity of the isotropic magnets is sensitive to the applied pressure in the CA-pressing and increases with increasing the pressure. The remanence of the anisotropic magnet increases with increasing the degree of deformation, and it results in the increase of a maximum energy Product. The best magnetic Properies of the isotropic and anistropic magnet are B$\sub$r/= 8.7 kG, $\sub$i/H$\sub$c/= 16.9 kOe, (BH)$\sub$max/= 16.5 and B$\sub$r/= 13.6 kG, $\sub$i/H$\sub$c/= 10.9 kOe, (BH)$\sub$max/= 44.2 MGOe, respectively.

• Journal of Magnetics
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• v.2 no.3
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• pp.67-71
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• 1997

A new hot-forming process has been studied to produce anisotropic Nd-Fe-B based magnets from melt-spun ribbons. The ribbon fragments were inserted in a Cu tube and hot-deformed together with one-stroke. At a height reduction ratio of 0.44, the melt-spun ribbons were densified into a magnet with a density of 7.14 g/cm3, and showed a (BH)max of 14.6 MGOe. With further deformation, the magnets were plastically deformed with Cu tubes in the lateral direction, and crystallographic anisotropy was introduced. The magnets with a height reduction ratio of 0.75 exhibited magnetic properties of (BH)max = 32.1 MGOe, Br = 11.7 kG, and iHc = 10.6 kOe. This process shows the possibility that the conventional hot-pressing and subsequent die-upsetting for anisotropic magnets can be simplified into a one-step process.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.232-233
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• 2002

Nanostructed high energy Nd-Fe-B based bulk magnet can be prepared by hot-working process (hot press and die-upset) from melt-spun amorphous or nanocrystalline powder.[1] Recently, we have investigated a modified method, current-applied pressure-assisted (CAPA) process, to produce nanocrystalline isotropic and anisotropic NdFeB magnets. The process consists of current-applied pressing the melt-spun powders to obtain isotropic precursor subsequent current-applied deforming the precursor to obtain textured magnet.[2-3] (omitted)

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.9-15
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• 2024

Nd-Fe-B permanent magnets have been utilized on various industrial fields such as electric vehicles, generator, robots with actuator, etc, due to their outstanding magnetic properties even 10 times better than conventional magnets. Recently, there are many researches that report magnetic properties improved by controlling microstructure through adjusting alloying elements or conducting various processing. Especially, post-sintering annealing (PSA) can significantly improve the coercivity by modifying the distribution and morphology of Nd-rich phase which formed at grain boundaries. In this study, Nd-Fe-B sintered magnets were subjected to primary heat treatment followed by secondary heat treatment at 460℃, 500℃, and 540℃ to investigate the changes in microstructure and magnetic properties with the secondary heat treatment temperature. EBSD analysis was conducted to compare anisotropic characteristics. Through the SEM and TEM observation for analyzing the morphology and distribution of Nd-rich phase, we investigated the relationship between microstructure and magnetic properties of sintered Nd-Fe-B magnets.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.208-209
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 1996.10a
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• pp.58-59
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• 1996

• Journal of the Korean Magnetics Society
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• v.12 no.3
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• pp.88-93
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• 2002

Rapidly solidified NdFeB powders were mixed with fine powders of pure metal elements before CA-press employed to obtain a fully dense isotropic precursor. Subsequently, the precursor was deformed by CA-deformation to obtain an anisotropic magnet. The CA-deformed anisotropic NdFeB magnets with 0.3 wt.% Zn or Sn exhibited the coercivities about 80% higher (11.4. and 11.2 kOe, respectively) than that (6.4 kOe) of the additive-free magnet.