Combination strategy for high-performance Sm(CoFeCuZr)z sintered permanent magnet: Synergistic improvement of the preparation process

Yang, Jianjun; Zhang, Dongtao; Zhang, H. G.; Li, Yuqing; Meng, Chengzhen; Teng, Yuan; Liu, Weiqiang; Xu, Xiaochang

doi:10.1016/j.actamat.2023.118901

Cited by 10 publications

(6 citation statements)

References 35 publications

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“…For all strip cast alloys, however, the phase distribution changed substantially to consist predominantly of the metastable 1:7H phase with small amounts of 1:5H phase and trace 2:17R phase. Due to the substantially increased cooling rate, the microstructure typically consisted of a nucleation zone where the melt started to solidify in contact with the wheel and columnar growth along the thermal gradient from the wheel side of the flake towards the free side, similar to that demonstrated by Meng et al [19] and Yang et al [20]. However, in a number of flakes, there were regions where the cooling rate was not sufficient to maintain columnar growth, resulting in non-directional growth towards the free side of the flake and elemental segregation similar to that observed in the as-received cast alloy.…”

Section: Discussionmentioning

confidence: 52%

“…Therefore, an alloy consisting of columnar grains would likely be more beneficial to magnet production than the fine, equiaxed grains produced in this work [19]. Yang et al [20] investigated the effect of strip casting wheel speed as a part of a larger study on magnet manufacture. They found that slower wheel speeds were more conducive to forming a microstructure suitable for magnet manufacture; however, they were not aiming for direct production of the 1:7H phase and were completing the entire manufacturing route as would be used for cast ingots containing heavy elemental segregation.…”

Section: Introductionmentioning

confidence: 99%

“…They found that slower wheel speeds were more conducive to forming a microstructure suitable for magnet manufacture; however, they were not aiming for direct production of the 1:7H phase and were completing the entire manufacturing route as would be used for cast ingots containing heavy elemental segregation. Whilst this showed very promising results from a magnetic point of view, it did not focus on direct production of the metastable 1:7H phase [20]. Yang et al [21] investigated hydrogen decrepitation of strip cast alloys similar to those presented in [20].…”

Section: Introductionmentioning

confidence: 99%

“…Whilst this showed very promising results from a magnetic point of view, it did not focus on direct production of the metastable 1:7H phase [20]. Yang et al [21] investigated hydrogen decrepitation of strip cast alloys similar to those presented in [20]. However, the micrograph showing the full cross-section of the alloy showed a rough surface that solidified in contact with the wheel, with a small nucleation zone and predominantly non-directional or equiaxed growth.…”

Section: Introductionmentioning

confidence: 99%

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Strip Casting of Sm2TM17-Type Alloys for Production of the Metastable SmTM7 Phase

Sheridan,

Gresle-Farthing,

Appleby

et al. 2024

Metals

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Conventional book casting of Sm2TM17-type alloys (where TM = Co, Fe, Cu, Zr) leads to a coarse, highly segregated microstructure, predominantly due to the slow, variable cooling rate from the mould surface towards the centre of the ingot. These cast alloys require a long homogenisation treatment to remove this segregation and develop a super-saturated, metastable SmTM7-type hexagonal phase. This SmTM7 phase is a vital precursor phase required during magnet production to develop the complex cellular structure responsible for high magnetic properties. In this work, strip casting was employed to facilitate rapid solidification to develop thin flakes (<0.5 mm thick) with a columnar grain structure. Rapid cooling has the potential to produce a homogenous microstructure consisting predominantly of the metastable SmTM7 phase. This could remove or significantly reduce the need for the energy-intensive homogenisation treatment usually required in conventional magnet manufacture. This paper investigates the effect of wheel speed (and hence cooling rate) on flake thickness, microstructure, and phase balance of the cast alloys. It was shown that for wheel speeds between 1.1 and 3.0 m/s, the microstructure showed large variation; however, in all cases, evidence of the columnar SmTM7 phase was presented. The adhesion between the melt and the wheel was deemed to be critical for the nucleation and subsequent columnar growth of SmTM7 grains, where the wheel speed controlled both the flow of the alloy onto the wheel and the thickness of the resultant flake. It was determined that in order to achieve a homogenous columnar SmTM7 structure, the maximum flake thickness should be limited to 270 μm to avoid the formation of equiaxed Sm2TM17 grains through insufficient cooling.

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Section: Discussionmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Strip Casting of Sm2TM17-Type Alloys for Production of the Metastable SmTM7 Phase

Sheridan,

Gresle-Farthing,

Appleby

et al. 2024

Metals

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show abstract

“…The elimination of GBP is attributed to the effect of grain boundary diffusion from the perspective of diffusion dynamics, which has been reported by related literatures. [39,40] Therefore, it is not discussed here in this work.…”

Section: Planar Z Phase Enhancement Mechanism Via Solid Solution and ...mentioning

confidence: 99%

High‐Remanence Fe‐Rich 2:17‐Type Sm–Co Sintered Magnets Mediated via Multiscale Microstructure

Xi,

Zhang,

et al. 2024

Adv Eng Mater

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Realizing high remanence in Fe‐rich 2:17‐type Sm‐Co sintered magnets remains a challenge when Fe content exceeds 23 wt.%. Here, a record remanence of 12.42 kGs has been obtained by multi‐scale microstructure regulation strategy, based on co‐optimization from pulverizing treatment to solid solution and aging treatment. The density of sintered magnet is significantly enhanced by refining magnetic powders using the ball milling to reduce the porosity. Grain boundary precipitation phase has been eliminated via prolonging solid solution time, together with reduced Fe concentration in the cell boundaries, due to increased proportion of defected 1:3R planar Z phase. Furthermore, the proportion of 1:3R planar Z phase has been increased by greatly reducing the 2:17R’ phase during appropriately isothermal aging temperature to reduce Fe concentration in cell boundaries and increases the remanence of the magnet. Our studies deepen the understanding of the correlation among process, microstructure, and remanence, guiding the preparation of Fe‐rich 2:17‐type Sm‐Co sintered magnets with high magnetic performance.This article is protected by copyright. All rights reserved.

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Large Coercivity and High Remanence in Iron‐Rich 2:17‐Type SmCo Magnets:Effect of Dislocation on Solid‐Solution Precursors

Hu,

He,

Liu

et al. 2024

Adv Funct Materials

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Iron‐rich 2:17‐type SmCo magnets are expected to achieve high performance and relatively low cost. However, inhomogeneous cellular structures usually exist in iron‐rich magnets, resulting in a drastic reduction in coercivity and energy product. Herein, a strategy is proposed to regulate the dislocation by decreasing the Sm content and extending the solid‐solution duration in precursor of iron‐rich SmCo magnet. High‐density dislocations in precursor contributed to 1:5H nucleation, leading to uniform cellular structures in final magnets. As a result, a remarkable intrinsic coercivity of 1.50 T and one of the highest remanences (1.24 T) are simultaneously achieved in the iron‐rich Sm25Co42Fe26Cu5Zr2 (wt%) magnet. This study provides valuable insights into the design and development of iron‐rich 2:17‐type SmCo magnets.

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Combination strategy for high-performance Sm(CoFeCuZr)z sintered permanent magnet: Synergistic improvement of the preparation process

Cited by 10 publications

References 35 publications

Strip Casting of Sm2TM17-Type Alloys for Production of the Metastable SmTM7 Phase

Strip Casting of Sm2TM17-Type Alloys for Production of the Metastable SmTM7 Phase

High‐Remanence Fe‐Rich 2:17‐Type Sm–Co Sintered Magnets Mediated via Multiscale Microstructure

Large Coercivity and High Remanence in Iron‐Rich 2:17‐Type SmCo Magnets:Effect of Dislocation on Solid‐Solution Precursors

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