On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study

Zhou, Lin; Guo, Wei; Poplawsky, Jonathan D.; Ke, Liqin; Tang, Wei; Anderson, Iver E.; Kramer, M. J.

doi:10.1016/j.actamat.2018.04.042

Cited by 32 publications

(7 citation statements)

References 22 publications

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“…Accordingly, upon cooling to below 1200 • C, a face center cubic (FCC) gamma (γ) phase is formed in the temperature range of 1175-850 • C [23][24][25]. The γ phase, which is formed in the temperature range of 1175-850 • C, transforms to α γ below 860 • C. When it is cooled to below 850 • C, the α phase spinodally decomposes into α 1 (BCC-B2) and α 2 (BCC L2 1 ) [26]. The alloying elements Ti, Co (up to 35 wt.%), and Nb (up to 2 wt.%) improve the coercivity, remanence, and BH max by increasing the volume fraction of the α 1 phase [27][28][29][30].…”

Section: Alloy (Castmentioning

confidence: 99%

Additively Manufactured Alnico Permanent Magnet Materials—A Review

Dussa,

Joshi,

Sharma

et al. 2024

Magnetism

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Additive manufacturing offers manufacturing flexibility for intricate components and also allows for precise control over the microstructure. This review paper explores the current state of the art in additive manufacturing techniques for Alnico permanent magnets, emphasizing the notable advantages and challenges associated with this innovative approach. Both the LPBF and L-DED processes have demonstrated promising results in fabricating Alnico with magnetic properties comparable with conventionally processed samples. The optimization of process parameters successfully reduced porosity and cracking in the LPBF processing of Alnico. The review further explored the significance of additive manufacturing process parameter optimization in managing the temperature gradient and solidification rate for a desired microstructure and enhanced magnetic properties. Other potential additive manufacturing methods suitable for the fabrication of Alnico were discussed, along with the challenges associated with the process. The insights provided also highlight how additive manufacturing holds the potential to replace post-processing techniques like solutionization, magnetic annealing, and tempering often necessary in Alnico production.

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Section: Alloy (Castmentioning

confidence: 99%

Additively Manufactured Alnico Permanent Magnet Materials—A Review

Dussa,

Joshi,

Sharma

et al. 2024

Magnetism

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“…Depending on how the main hard-magnetic phase is generated, permanent magnets can be divided into two types: (i) formed by solidification, including Nd-Fe-B magnets and ferrites; (ii) formed by solid-state phase transformation, including Al-Ni-Co magnets, Sm2Co17-type magnets, ThMn12-type magnets and L10-type magnets. In Al-Ni-Co systems, the shape anisotropy of cubic Fe-Co phase is the origin of high coercivity, this phase is generated by a spinodal decomposition reaction 66 . For Sm2Co17-type magnets 67 , RETM12-type magnets 11 and L10-type magnets 39 , symmetry breaking is an apparent feature of the solid-state transformation for them, so twins are always accompanied with the formation of the final hard-magnetic products.…”

Section: Stb-surface Area Of Twin Boundarymentioning

confidence: 99%

Roadmap towards optimal magnetic properties in rare-earth-free L10-MnAl permanent magnets

Jia

et al. 2022

Preprint

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Twin defects deteriorate the magnetic properties in conventionally-fabricated L10-type and RETM12-type permanent magnets. Herein, we propose a strategy to suppress twins’ formation by decreasing the grain and/or particle sizes below a critical size Dt~300 nm, based on the stress relief mechanism resulting from the balance of volume/surface energy. Twin-free monocrystalline nanoparticles smaller than Dt were synthesized using a comprehensive spectrum of methods for preparing field-aligned polymer bonded magnet with high texture. We propose here a roadmap for selecting the best route for manufacturing high-performance rare-earth free MnAl magnets, depending on their grain/particle size. The dependence of coercivity on grain/particle sizes shows that optimal coercivity can be reached within the range of 50-200 nm, meanwhile, twin-free microstructure is realized which allows ultrahigh remanence by field induced texture. The results reported here can be applied to other twin-containing permanent magnet compounds, offering opportunities to drastically increase their texture and maximal energy products.

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“…The formation of compositionally modulated microstructures was able to enhance the mechanical and magnetic properties of HEAs. [ 24 , 25 , 26 ] Inspired by these studies, we attempted to investigate whether these physical metallurgy strategies in HEA are sufficient to manipulate their dealloyed porous architecture with enhanced electrocatalytic properties.…”

Section: Introductionmentioning

confidence: 99%

Design of Hierarchical Porosity Via Manipulating Chemical and Microstructural Complexities in High‐Entropy Alloys for Efficient Water Electrolysis

Liu

et al. 2022

Advanced Science

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Achieving a porous architecture with multiple‐length scales and utilizing the synergetic effects of multicomponent chemicals bring up new opportunities for further improving the electrocatalytic performance of nanocatalysts. Herein, the synthesis of a self‐supported hierarchical porous electrocatalyst based on a high‐entropy alloy (HEA) containing multiple transitional metals via physical metallurgy and dealloying strategies is reported. Microscale phase separation and nanoscale spinodal decomposition are modulated in a highly concentrated FeCoNiCu HEA, which makes it possible to obtain a porous structure with different length scales, i.e., relatively large porous channels formed by removing one separated phase and ultrafine mesopores obtained from leaching out one decomposition phase. The resultant hierarchical porous HEA exhibits superior water splitting performance, which takes full advantage of the enlarged surface area offered by the bi‐continuous mesoporous structure with the exceptional intrinsic reactivity originating from the synergetic electronic effects of the different components in alloying. Moreover, the microscale porous structure plays an important role in the significantly improved mass transportation, as well as the durability during electrocatalysis. This effective strategy that simultaneously utilizes the chemical and microstructural advantages of HEAs opens up a new avenue for developing HEA‐based, high‐performance porous electrocatalysts for various energy conversion/store applications.

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On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study

Cited by 32 publications

References 22 publications

Additively Manufactured Alnico Permanent Magnet Materials—A Review

Additively Manufactured Alnico Permanent Magnet Materials—A Review

Roadmap towards optimal magnetic properties in rare-earth-free L10-MnAl permanent magnets

Design of Hierarchical Porosity Via Manipulating Chemical and Microstructural Complexities in High‐Entropy Alloys for Efficient Water Electrolysis

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