Ga added Nd-Fe-B sintered and die-upset magnets

Tokunaga, M.; Nozawa, Y.; Iwasaki, K.; Endoh, M.; Tanigawa, S.; Harada, Hideki

doi:10.1109/20.42365

Cited by 38 publications

(9 citation statements)

References 11 publications

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“…The increase of the Q parameter in DU2162, the sample doped with both cobalt and gallium, relative to that of DU1418, is consistent with a certain amount of exchange decoupling between the grains that serves to produce a greater density of "effective domains". Many researchers (40)(41)(42)(43) believe that when gallium is added to 2-14-1-based magnets it segregates to the grain boundary phase; such a segregation would be expected to decrease the intergranular coupling by diluting the magnetic properties of the intergranular phase. I m, hvesb 'gations Into Coerc ivip Mec hanisms in "Exchanee-SDrine" Nd-Fe-B Allovs Some researchers (44) believe that the next generation of permanent magnets may not stem from an as-yet undiscovered intermetallic composition but rather will be a magnetic composite comprised of an aligned hard-magnet skeleton phase filled in with a soft-magnetic phase of high saturation magnetizgtion, known as an aligned "exchange-spring" magnet (10).…”

Section: Resultsmentioning

confidence: 99%

Factors affecting coercivity in rare-earth based advanced permanent magnet materials

Lewis

Sellers

Panchanathan³

1997

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The relationships that link microstructural properties of advanced permanent magnet materials with magnetic properties such as the coercivity are often difficult to quantifv, especially in materials with nano-scale structures. Recent work on RE2Fel4B-based powders fabricated with rapidsolidification techniques such as inert gas atomization (IGA) and melt-spinning provide insight into the nanostructural features which affect the acquisition and stability of coercivity. In all cases the coercivity is found to be a function of both the scale of the constituent microstructure and of the presence and distribution of minor phases.Research was performed under the auspices of the U.S.

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Section: Resultsmentioning

confidence: 99%

Factors affecting coercivity in rare-earth based advanced permanent magnet materials

Lewis

Sellers

Panchanathan³

1997

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“…In single-powder magnets the Ga concentration within the grains is in the order of 80%-90% of the nominal input 21,22 . This means that in the two-powder magnets a larger amount of Ga is able to form the required intergranular phases.…”

Section: Discussionmentioning

confidence: 99%

Two-powder Nd2Fe14B magnets with DyGa-addition

Groot

Buschow

Boer

et al. 1998

Journal of Applied Physics

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Magnetic and structural properties of sintered NdFeB magnets with addition of various amounts of DyGa as a separate powder are studied and compared with single-powder magnets of the same nominal composition. When the magnets are annealed above 640°C, the coercivity decreases strongly as compared to magnets annealed below 640°C. Decomposition of the ␦ phase ͑Nd 6 Fe 14Ϫx Ga x ) accompanies this drop. Measurements of coercivity as a function of temperature show that the decomposition of the ␦ phase does not increase the effective demagnetization factor, but enlarges either the magnetic inhomogeneous region at the grain surface or the exchange coupling between the grains. Line faults, which are present within the Nd 2 Fe 14 B grains when the magnet is annealed below 640°C, do not act as pinning centers. Phase analysis and diffusion profiles of the Dy and Ga concentration within the grains are made using electron probe micro-analysis. This shows that Ga forms Nd 3 Ga 2 and Nd 6 Fe 12.7 Ga 1.3 as intergranular phases. Its concentration within the ⌽ phase is significantly lower than in the ⌽ phase of single-powder magnets. At 1090°C, a diffusion coefficient for Ga of Dϭ2.5Ϯ0.1ϫ10 Ϫ15 m 2 /s is found. Dy is shown only to be present in that part of the Nd 2 Fe 14 B grain which has precipitated from the liquid during sintering. At the boundary of the Dy-free center and the outer part of the grain, an increased Dy concentration is found.

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“…The range of magnetic properties achieved by melt-spun anisotropic die-upset (MQ3) and isotropic hot-pressed (MQ2) materials are illustrated in figure 10. The alloy composition tends to dictate the position of a particular magnet on this chart [33][34][35]. The amount and type of rare earth component, as well as minor additions of elements such as gallium, control the magnet's performance to a certain extent.…”

Section: Increasing the Remanence Of Hot-deformed Magnetsmentioning

confidence: 99%

Dysprosium-free melt-spun permanent magnets

Brown¹,

Wu²,

He³

et al. 2014

J. Phys.: Condens. Matter

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Melt-spun NdFeB powders can be formed into a number of different types of permanent magnet for a variety of applications in electronics, automotive and clean technology industries. The melt-spinning process produces flake powder with a fine uniform array of nanoscale Nd2Fe14B grains. These powders can be net-shape formed into isotropic polymer-bonded magnets or hot formed into fully dense magnets. This paper discusses the influence of heavy rare earth elements and microstructure on the magnetic performance, thermal stability and material cost of NdFeB magnets. Evidence indicates that melt-spun nanocrystalline NdFeB magnets are less dependent on heavy rare earth elements for high-temperature performance than the alternative coarser-grained sintered NdFeB magnets. In particular, hot-pressed melt-spun magnets are an attractive low-cost solution for applications that require thermal stability up to 175-200 °C.

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Ga added Nd-Fe-B sintered and die-upset magnets

Cited by 38 publications

References 11 publications

Factors affecting coercivity in rare-earth based advanced permanent magnet materials

Factors affecting coercivity in rare-earth based advanced permanent magnet materials

Two-powder Nd2Fe14B magnets with DyGa-addition

Dysprosium-free melt-spun permanent magnets

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