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  • Articles  (26)
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  • Articles  (26)
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 67 (1963), S. 2008-2015 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6907-6911 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We used consolidation (hot pressing) and deformation (die upsetting) techniques to produce magnetically anisotropic permanent magnets from melt-spun PryCo100−y−xCx alloys. The primary phase in these magnets (16≤y≤24 at. %) was the hexagonal PrCo5 phase. The greatest alignment was obtained for low-carbon compositions (0≤x≤2 at. %); in particular, Pr18Co81C produced a remanence of ∼8.7 kG and an energy product of 16.9 MG Oe. The addition of 1 at. % carbon enhanced the coercivity (Hcl≈5.9 kOe) by nearly 80% compared to the carbon-free composition (Hcl≈3.3 kOe). Higher carbon levels (x≥4 at. %) resulted in even larger coercivities (Hcl≥10 kOe) but were accompanied by significantly lower remanences (Br≈6 kG).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5751-5756 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The best starting materials for die-upset magnets are moderately overquenched melt-spun ribbons of Nd-Fe-B alloys with ∼20 at. % more rare earth than stoichiometric Nd2Fe14B. Remanence increases with increasing die-upset (DU) level, reaching a maximum of 13.5 kG at 70% DU for ternary Nd-Fe-B magnets, beyond which cracking limits performance. Remanence is also limited by nonuniform deformation, particularly for moderately die-upset magnets. Heat treatments, dysprosium substitutions, or low-level additives can be used to compensate for the decreases in coercivity which accompany increases in die-upset level. By die upsetting in stages and removing misaligned surfaces, a large Nd-Fe-Co-B-Ga magnet (∼30 g) has been produced with both a high remanence (14.2 kG) and a high-energy product (48.5 MG Oe).
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6444-6446 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Melt-spun Nd-Fe-B ribbons are limited to remanences of about 8 kG by the random orientation of the Nd2Fe14B grains. Hot deformation (die upsetting) causes these grains to reorient with the c axis aligned along the press direction, resulting in a 50% increase in the remanence (12 kG). Previously others have produced magnetically hard melt-spun ribbons containing the isostructural phase Nd2Fe14C which, like the boride ribbons, were isotropic. By adjusting alloy stoichiometry and process variables, it is possible to die upset Nd-Fe-C magnets with properties similar to Nd-Fe-B magnets. As with the boride magnets, the remanences of the die-upset Nd-Fe-C magnets were enhanced about 45% relative to the isotropic precursor. However, the remanences of die-upset carbide magnets were limited to about 10 kG due to the lower saturation magnetization of the Nd2Fe14C phase and higher levels of impurity phases.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5826-5828 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In general, the stoichiometry of melt-spun ribbons and subsequent hot-worked Nd-Fe-B magnets derives from the composition of the starting ingot. We have shown, however, that it is possible to introduce small amounts of powdered metals into the ribbons after the ingot has been melt spun. Many elements, when mixed with the ribbons as a fine powder and then hot pressed, have been observed to diffuse into nearby ribbons, and in some cases (Cd, Cu, Au, Ir, Mg, Ni, Pd, Pt, Ru, Ag, and Zn) the elements diffused fairly evenly throughout the Nd-Fe-B ribbon matrix. These eleven elements significantly enhanced the coercivity of die-upset magnets, with the highest coercivity observed with the addition of zinc (∼16 kOe).
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2659-2664 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallographic alignment quality of anisotropic magnetic materials made from die-upset Nd2Fe14B (MQ-III) materials was determined using a phenomenological analysis of θ-2θ x-ray diffraction spectra. This analysis consisted of fitting a calculated diffraction spectrum for aligned Nd2Fe14B to an observed spectrum collected on a bulk MQ-III slab oriented with the c-axis alignment parallel to the direction normal to the surface of the slab. The calculated spectrum was then used as a standard for intensity shifts of diffraction peaks corresponding to crystallographic reorientation from random to c-axis alignment. Intensity shifts for other samples for Nd2Fe14B materials having various degrees of c-axis alignment were determined and compared to the standard shifts giving an alignment factor representing the nature and extent of the crystallographic alignment in the sample.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4208-4213 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to optimize the magnetic properties of die-upset Pr-Fe-B magnets, we have systematically altered alloy compositions, including partial substitution of cobalt and neodymium, and low-level additions of gallium. In general, the remanences of Pr-Fe-B die-upset magnets were lower by ∼1 kG, and coercivities were higher by ∼4 kOe, than analogous Nd-Fe-B magnets. The microstructure of the Pr-Fe-B die-upset magnets was similar to Nd-Fe-B magnets. Both systems are two phase, consisting of oriented flat platelet-shaped grains of 2-14-1 separated by a rare earth-rich intergranular phase. The intergranular phase is thicker for the Pr-Fe-B magnets, resulting in enhanced magnetic domain wall pinning and increased coercivity. Even higher coercivities were obtained with small amounts of cobalt substitution (≤5 at. % of the transition metal) and by very low-level additions of gallium (≤0.5 at. %). The largest remanence (Br=13.7 kG) for a Pr-based 75% die-upset magnet was obtained with the alloy (R13TM81B6)0.9975Ga0.25, where R=(Pr0.8Nd0.2) and TM=(Fe0.95Co0.05).
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6232-6234 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We prepared die-upset Nd-Fe-Co-B magnets from melt-spun ribbon powders which were a series of blends of two ribbon alloys. One alloy was always ternary Nd-Fe-B (no cobalt), and in the other cobalt replaced up to half of the iron. Differential scanning calorimeter measurements revealed that during hot working, the cobalt diffused across ribbon boundaries, effectively redistributing the transition metal concentration throughout the magnet. Instead of anomalies indicating the Curie temperatures of the two original ribbon compositions, we found a single transition consistent with the average cobalt concentration in the magnet. However, the transition was broader than expected, suggesting that the homogenization was incomplete. These results are new evidence of massive diffusion occurring between ribbons, changing the microstructure and facilitating the deformation of the otherwise rigid 2-14-1 magnet.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2601-2603 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated novel magnetostrictive composites consisting of SmFe2 embedded in an Fe or Al matrix which feature high magnetostriction and good mechanical strength. Hot pressed composites of 50% SmFe2/50% Fe or Al by volume have magnetostrictive strains parallel to the applied magnetic field, λ(parallel), between −280 and −440 ppm when consolidated at 610 (Fe) or 540 °C (Al). One unique feature of this work is the production of the magnetostrictive SmFe2 component by melt spinning; ribbon-based composites with Al combine significant magnetic coercivity, Hci=3 kOe, with high magnetostriction (λ(parallel)=−280 ppm). Unlike their brittle SmFe2 parent materials, the composites are easily machinable. © 1997 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2252-2254 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rapidly solidified Nd-Fe-B ribbons were crushed and mixed with a fine powder (10–100μm) of a pure element before hot working into fully dense anisotropic magnets. At the high temperatures and pressures required for densification some additives diffused throughout the ribbon matrix and presumably into the neodymium-rich phase surrounding the Nd2Fe14B grains. In small concentrations (0.5–0.8 wt%), zinc, copper, and nickel additions enhanced the coercivities of die-upset magnets by 100%, 77%, and 53%, respectively. Additives which did not diffuse thoroughly, such as manganese, had no measurable effect on the coercivities.
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