Magnetic and structural properties of spark plasma sintered nanocrystalline NdFeB-powders

Wüest, H.; Bommer, Lars; Weissgaerber, Thomas; Kieback, Bernd

doi:10.1016/j.jmmm.2015.05.014

Cited by 15 publications

(3 citation statements)

References 17 publications

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“…Therefore, the oxygen for internal oxidation must have been already present inside the specimen or on the surfaces of the melt-spun powder in the initial state. Wuest et al described a similar dissociation behavior of the Nd 2 Fe 14 B phase into fine precipitations of Ndrich and Fe-rich phases during spark plasma sintering [25].…”

Section: Microstructurementioning

confidence: 79%

Electro-discharge sintering of nanocrystalline NdFeB magnets: process parameters, microstructure, and the resulting magnetic properties

Leich

Röttger

Kuchenbecker

et al. 2020

J Mater Sci: Mater Electron

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This study investigates the compaction of nanocrystalline NdFeB magnet powder by electro-discharge sintering (EDS). On this account, process parameters, microstructure, and the associated magnetic properties of the EDS-densified nanocrystalline NdFeB specimens were investigated by varying the discharge energy EEDS and compression load pEDS. Although optimized process parameters could be evaluated, three different microstructures (fully densified zone, insufficiently densified zone, and melted zone) are present in the EDS-compacted specimens. Thereby, volume fractions of these formed three different microstructures determine the resulting mechanical and magnetic properties of the specimens. For all specimens, the intrinsic coercivity Hc,J deteriorates with increasing discharge energy, as the generated Joule heat leads to microstructural changes (grain growth, dissolution of magnetic phases), which reduces the magnetic properties. The compression load has less influence on the coercivity Hc,J, as it only affects the initial resistance of the pre-compacted powder loose. The residual induction Br deteriorates with increasing the discharge energy due to microstructural changes. An increase in the compression load pEDS results in an increase in the specimens’ density and thus promotes the residual induction Br.

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Section: Microstructurementioning

confidence: 79%

Electro-discharge sintering of nanocrystalline NdFeB magnets: process parameters, microstructure, and the resulting magnetic properties

Leich

Röttger

Kuchenbecker

et al. 2020

J Mater Sci: Mater Electron

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“…For conductive materials like Nd–Fe–B, indirect heating by thermal conduction is supported by direct Joule heating of the powder compact. FAST/SPS can be used to replace the hot‐pressing step resulting in isotropic Nd–Fe–B magnets as demonstrated, for example, by Wüst et al [ 49 ] Going a step further, FAST/SPS can be also used for die‐upsetting. Wang et al produced a Nd–Fe–B magnet with a remanence B r of 1.42 T, a coercivity H c i of 1234 kAm −1 , and a maximum energy product of 385.9 kJm −3 by FAST/SPS without exactly specifying experimental setup and parameters.…”

Section: Introductionmentioning

confidence: 99%

Nanocrystalline Nd–Fe–B Anisotropic Magnets by Flash Spark Plasma Sintering

et al. 2023

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Flash spark plasma sintering (flash SPS) is an attractive method to obtain Nd–Fe–B magnets with anisotropic magnetic properties when starting from melt‐spun powders. Compared to the benchmark processing route via hot pressing with subsequent die upsetting, flash SPS promises electroplasticity as an additional deformation mechanism and reduced tool wear, while maximizing magnetic properties by tailoring the microstructure—fully dense and high texture. A detailed parameter study is conducted to understand the influence of Flash SPS parameters on the densification and magnetic properties of commercial MQU‐F powder. It is revealed that the presintering conditions and preheating temperature before applying the power pulse play a major role for tailoring grain size and texture in the case of hot deformation via Flash SPS. Detailed microstructure and magnetic domain evaluation disclose the texture enhancement with increasing flash SPS temperature at the expense of coercivity. The best compromise between remanence and coercivity (1.37 T and 1195 kA m−1, respectively) is achieved through a combination of presintering at 500 °C for 120 s and preheating temperature of 600 °C, resulting in a magnet with energy product (BH)max of 350 kJm−3. These findings show the potential of flash SPS to obtain fully dense anisotropic nanocrystalline magnets with high magnetic performance.

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“…Recently, Spark Plasma Sintering (SPS) is being widely used as an alternative technique to consolidate fine-grained powders [6]. In the SPS, a pulsed electric current flows directly through the to be sintered powder, matrix and punches.…”

Section: Introductionmentioning

confidence: 99%

Consolidation Behavior and Magnetic Properties of Nanocrystalline Nd-Fe-B Magnets Prepared by Spark Plasma Sintering

Keller

Engerroff

Lopes

et al. 2017

MSF

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Spark Plasma Sintering (SPS) was studied as a means to consolidate Nd-Fe-B powders, previously subjected to grain refinement by HDDR (Hidrogenation–Disproportionation–Dessorption–Recombination). The sintering process was carried out under 60 MPa constant pressure, varying the maximum processing temperature from 500 °C to 900 °C with a holding time of 5 min. Densification was observed above 600 °C related to the melting of Nd-rich phase. The magnetic properties are clearly related to microstructure coarsening associated with the SPS temperature regime. A monotonic decrease for coercivity (Hcj) was observed as a function of maximum SPS operating temperature with values varying from maximum of 750 kA/m at 500 °C to less than 200 kA/m for SPS at 900 °C. Remanence (Br) and maximum energy product (BH)max showed optimum values for intermediate temperatures, since these properties benefit from the densification developed by SPS.

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Magnetic and structural properties of spark plasma sintered nanocrystalline NdFeB-powders

Cited by 15 publications

References 17 publications

Electro-discharge sintering of nanocrystalline NdFeB magnets: process parameters, microstructure, and the resulting magnetic properties

Electro-discharge sintering of nanocrystalline NdFeB magnets: process parameters, microstructure, and the resulting magnetic properties

Nanocrystalline Nd–Fe–B Anisotropic Magnets by Flash Spark Plasma Sintering

Consolidation Behavior and Magnetic Properties of Nanocrystalline Nd-Fe-B Magnets Prepared by Spark Plasma Sintering

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