Atomic scale understanding of the defects process in concurrent recrystallization and precipitation of Sm-Co-Fe-Cu-Zr alloys

Song, Xin; Ma, Tianyu; Zhou, Xianwei; Ye, Fan; Yuan, Tao; Wang, Jingdong; Yue, Ming; Liu, Feng; Ren, Xiaobing

doi:10.1016/j.actamat.2020.10.067

Cited by 56 publications

(19 citation statements)

References 48 publications

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“…The crystalline directions can be identified via further TEM characterizations, as shown in Figure 2(c 2 ) and (c 3 ). The micro-twinning structure typical of rhombohedral Sm 2 Co 17 with (001) as the twin plane can be observed, which is related to the ordered substitution of Sm atoms by Co-Co pairs along different directions in the crystal structure [35,36]. In addition, the regular shape and TEM observations indicate that the NPs are single crystals.…”

Section: Resultsmentioning

confidence: 84%

Morphology evolution of SmCox permanent magnetic nanoparticles

Dong

Wang

Liu

et al. 2021

Sci. China Phys. Mech. Astron.

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Sm-Co nanoparticles (NPs) are promising candidates for preparing superstable magnets and exchange-coupled nanocomposite magnets with unprecedented magnetic properties. However, the morphology evolution of the NPs remains unclear. Here, single crystalline SmCo x (x = 4.07, 4.79, 6.94, and 8.61) NPs with dimensions below the critical size of a single magnetic domain were synthesized. These NPs consist of Sm 2 Co 7 , SmCo 5 , and Sm 2 Co 17 phases with divergent typical morphologies. An evolution model for the different morphological characteristics was proposed based on phase-structure changes and surface-energy calculations using the density functional theory. The results show that these SmCo 4.79 NPs can be well aligned along the easy magnetization axis and exhibit an ultrahigh coercivity of 5.7 T, thus enabling to advance the control of NP morphology and to facilitate their use in superstable or nanocomposite magnets.

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Section: Resultsmentioning

confidence: 84%

Morphology evolution of SmCox permanent magnetic nanoparticles

Dong

Wang

Liu

et al. 2021

Sci. China Phys. Mech. Astron.

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“…The 1:5H precipitates usually occupy the {011} 2:17R pyramidal cell boundaries and the 1:3R lamellar precipitates usually occupy the {001} basal planes across the cells and cell boundaries [32,33,35]. Recent work has revealed that there is also a 2:17R' phase, the intermediate phase of 2:17R, having one faulted basal layer in the 2:17R lattice, which is usually observed at the cell edges [20]. In Fe-rich magnets, 1:3R, 2:7R, 5:19R, or their mixtures have also been observed at the grain boundaries [12,13,16,37,39].…”

Section: Resultsmentioning

confidence: 99%

“…The partial dislocation glides were diffusion-controlled. Thus, at the early decomposition stage, the successful nanoscale glides at the local regions will create 2:17R nanotwins whereas the incomplete glides will lead to SFs [ 20 ]. The growth of 2:17R variants is at the expense of reducing the basal SFs that are frequently observed at grain boundaries.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, at the early decomposition stage, the successful nanoscale glides at the local regions will Note that the transformation from 2:17H to 2:17R and the precipitation/growth of the 1:5H phase occurred simultaneously. As 2:17H has been deemed the precursor of 2:17R [20,44], the existence of 2:17R nanotwins and SFs (2:17R') can be understood in terms of the dislocation glides for the transformation from 2:17H to 2:17R by the glides of a/3 {001}-<120> partial dislocations. The partial dislocation glides were diffusion-controlled.…”

Section: Discussionmentioning

confidence: 99%

“…However, the magnets usually contain various types of microstructural deficiencies, which weaken the pinning force against DW motions locally and lead to an inhomogeneous demagnetization process as well as a poor squareness factor. These microstructural deficiencies include: (i) the intersections between 1:5H precipitates and the co-existing 1:3R precipitates [14], (ii) the cell edges that usually contain stacking faults (SFs) or the 2:17R' intermediate phase [20], (iii) the defect-aggregated cell boundaries (DACBs) free of the 1:5H phase [21], and (iv) the grain boundaries with sparser 1:5H cell boundary precipitates (i.e., larger cells) than the grain interiors and phase mixture of Zr-stabilized Sm n+1 Co 5n−1 (n = 2, 1:3R; n = 3, 2:7R; n = 4, 5:19R) precipitates that are magnetically softer than the 1:5H precipitates [15,[22][23][24][25][26][27]. Among them, the grain boundaries have been thought to be the primary demagnetization sites [5,28].…”

Section: Introductionmentioning

confidence: 99%

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Grain Boundary Evolution of Cellular Nanostructured Sm-Co Permanent Magnets

et al. 2021

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Grain boundaries are thought to be the primary demagnetization sites of precipitate-hardening 2:17-type Sm-Co-Fe-Cu-Zr permanent magnets with a unique cellular nanostructure, leading to a poor squareness factor as well as a much lower than ideal energy product. In this work, we investigated the grain boundary microstructure evolution of a model magnet Sm25Co46.9Fe19.5Cu5.6Zr3.0 (wt. %) during the aging process. The transmission electron microscopy (TEM) investigations showed that the grain boundary region contains undecomposed 2:17H, partially ordered 2:17R, 1:5H nano-precipitates, and a Smn+1Co5n-1 (n = 2, 1:3R; n = 3, 2:7R; n = 4, 5:19R) phase mixture at the solution-treated state. After short-term aging, further decomposition of 2:17H occurs, characterized by the gradual ordering of 2:17R, the precipitation of the 1:5H phase, and the gradual growth of Smn+1Co5n−1 compounds. Due to the lack of a defect-aggregated cell boundary near the grain boundary, the 1:5H precipitates are constrained between the 2:17R and the Smn+1Co5n-1 nano-sheets. When further aging the magnet, the grain boundary 1:5H precipitates transform into Smn+1Co5n-1 compounds. As the Smn+1Co5n-1 compounds are magnetically softer than the 1:5H precipitates, the grain boundaries then act as the primary demagnetization sites. Our work adds important insights toward the understanding of the grain boundary effect of 2:17-type Sm-Co-Fe-Cu-Zr magnets.

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Atomic‐Scale Transition Zones Determined Coercivity in Samarium‐Cobalt Based Permanent Magnets

Liu,

Wang,

et al. 2023

Adv Funct Materials

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SmCo‐based permanent magnets with nanocellular structure exhibit significant advantage for high‐temperature applications. Due to the lack of experimental intrinsic magnetic parameters and unclear nanocellular interface, a fully understanding on coercivity mechanism is still limited. Here the intrinsic magnetic properties of designed two single‐phase alloys representing nanocellular structure at various temperatures are acquired. Using 3D atom probe and high‐angle annular dark‐field scanning transmission electron microscopy, the existence of the nanoscale transition zones located at nanocellular interface is revealed. Moreover, the transition zones exhibiting high magnetocrystalline anisotropy is found to contribute dominantly to the coercivity. The calculated coercivity via micromagnetic simulation considering transition zones agrees well with the tested coercivity at various temperatures. This knowledge deepens the fundamental understanding on coercivity mechanism.

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Atomic scale understanding of the defects process in concurrent recrystallization and precipitation of Sm-Co-Fe-Cu-Zr alloys

Cited by 56 publications

References 48 publications

Morphology evolution of SmCox permanent magnetic nanoparticles

Morphology evolution of SmCox permanent magnetic nanoparticles

Grain Boundary Evolution of Cellular Nanostructured Sm-Co Permanent Magnets

Atomic‐Scale Transition Zones Determined Coercivity in Samarium‐Cobalt Based Permanent Magnets

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