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  • 1
    Electronic Resource
    Electronic Resource
    Die-upset Pr-Fe-B-type magnets from melt-spun ribbons (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4208-4213 
    Details
    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).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356006
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  • 2
    Electronic Resource
    Electronic Resource
    Die-upset Nd-Fe-Co-B magnets from blends of dissimilar ribbons : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6232-6234 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358290
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  • 3
    Electronic Resource
    Electronic Resource
    Neutron irradiation study of Nd-Fe-B permanent magnets made from melt-spun ribbons (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5305-5307 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Radiation-induced changes in the magnetization of sintered Nd-Fe-B permanent magnets are known to vary widely among specimens produced by different manufacturers. Samples of Nd-Fe-B MAGNEQUENCH magnets, which are made from melt-spun ribbons, have not been studied and show a much reduced sensitivity to neutron irradiation than do sintered Nd-Fe-B magnets. All melt-spun ribbon-based MAGNEQUENCH magnets, i.e., epoxy-bonded, hot-pressed, and die-upset magnets, show essentially the same slow decrease in magnetic remanence with neutron dose. Measurements of the open-circuit remanence Br/Br 0 at various times during the irradiation show a decay of only 1.5% of the preirradiated value for the MAGNEQUENCH magnets after 1 h of irradiation, or a dose of 1.4×1016 neutrons/cm2, compared to a 4.6% drop in remanence for the best sintered Nd-Fe-B magnet (Sumitomo 30H) with the same irradiation dose. Moreover, after 5.3 h of irradiation, the remanence drops by only 3% for the MAGNEQUENCH magnets. Magnets made from melt-spun ribbons are thus the least sensitive to neutron irradiation so far measured for Nd-Fe-B permanent magnets, but are somewhat more sensitive than samarium-cobalt magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342400
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  • 4
    Electronic Resource
    Electronic Resource
    Die-upset Nd2Fe14 M magnets (M=B and C) : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6444-6446 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349925
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  • 5
    Electronic Resource
    Electronic Resource
    Die-upset PrCo5-type magnets: Enhanced coercivities : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6637-6639 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rare-earth–cobalt alloys have been melt spun, yielding ribbons whose major phase was the hexagonal PrCo5 phase. Fully dense hot-pressed magnets with essentially isotropic magnetic properties have been formed by consolidating the ribbons at high temperatures and pressures. The hot-pressed precursor was then subjected to hot deformation or die upsetting, thereby inducing partial alignment of the c axis along the press direction. The resulting magnets had remanences approaching ∼75% of the saturation magnetization of the hexagonal PrCo5 phase. Three approaches were used to optimize the coercivity of the die-upset magnets: (i) replacing small amounts of cobalt with carbon; (ii) partially substituting samarium for the praseodymium; and (iii) high-temperature heat treatment followed by a thermal quench. Coercivities near ∼20 kOe were achieved with thermally quenched die-upset (Pr0.6Sm0.4)18Co81C magnets, while maintaining remanences above 8 kG.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356879
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  • 6
    Electronic Resource
    Electronic Resource
    High-remanence rapidly solidified Nd-Fe-B: Die-upset magnets (invited) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5751-5756 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.353563
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  • 7
    Electronic Resource
    Electronic Resource
    Crystallographic alignment analysis of Nd2Fe14B materials using standard x-ray powder diffraction spectra (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2659-2664 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.351567
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  • 8
    Electronic Resource
    Electronic Resource
    Die-upset PrCo5-type magnets from melt-spun ribbons (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6907-6911 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.355336
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  • 9
    Electronic Resource
    Electronic Resource
    Diffusion-alloyed additives in die-upset Nd-Fe-B magnets : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5826-5828 
    Details
    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).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347862
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  • 10
    Electronic Resource
    Electronic Resource
    Processing effects on the magnetostrictive and physical properties of SmFe2/metal composites : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7252-7254 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hot pressed SmFe2/Fe and SmFe2/Al composites combine the large magnetostriction of SmFe2 with the mechanical robustness of the Fe or Al matrix. Here we report the dependence of the magnetostriction, density, and mechanical hardness on processing parameters, specifically on the SmFe2 volume fill fraction and the consolidation temperature. The magnetostriction increases monotonically with increasing SmFe2 content, but both the density and hardness decrease; low fill fraction composites are within 10% of theoretical density and have hardnesses of 40–85 Rockwell B, whereas hot pressed SmFe2 powder alone has high porosity (exceeding 30%) and is too soft to register on the Rockwell B hardness scale. The best combination of properties lies in the range of 40%–60% SmFe2. Similar competition between magnetostriction and physical properties is observed as a function of the temperature used to consolidate the samples. The magnetostriction falls slowly as the hot press temperature increases, probably as a result of chemical reaction between the SmFe2 phase and the matrix metal. On the other hand, higher temperature improves the consolidation, resulting in higher density and hardness. These results demonstrate that the magnetostrictive and physical properties of SmFe2 composites can be tailored by adjusting the fill fraction and processing temperature. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367699
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