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  • 1
    Electronic Resource
    Electronic Resource
    The microstructures and magnetic properties of some cast and annealed Pr-Fe-Cu-B alloys (abstract) : 37th annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6497-6497 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper reports the results of investigations of the microstructures and magnetic properties of some cast and annealed Pr-Fe-Cu-B alloys represented by the formulas PrxFe94.3−xCu2.0B3.7, Pr20.5Fe75.8−xCuxB3.7, and Pr20.5Fe77.5−xCu2.0Bx. Microstructural examination of these alloys showed that most of them exhibited Pr2Fe14B plate-like grains with the c axis perpendicular to the plate surface and there was c-axis alignment in the plane perpendicular to the predominant cooling direction. SEM examination of the alloys showed that the copper was concentrated in the intercrystalline regions and only trace quantitiies (〈0.4 at. %) of copper were detected in the Pr2Fe14B phase. A eutectic mixture and a needle-like phase were observed in the intercrystalline regions. The permanent magnetic properties of the alloys, subject to various casting conditions and heat treatments, were investigated and enhanced properties were observed perpendicular to the predominant cooling direction. The largest (BH)max value (70 kJ m−3) was achieved for the Pr20.5Fe73.8Cu2.0B3.7 alloy after annealing at 1000 °C for 5 h to remove the free iron. An improvement in the intrinsic coercivity of 73% was observed for this alloy on annealing for 3 h at 500 °C. Attempts have been made to correlate the permanent magnetic properties of the alloys with their corresponding microstructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352592
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic properties of the sintered magnets produced from a Nd-Fe-B-Cu-type material : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6453-6455 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of Nd17Fe76.5B5Cu1.5-type sintered magnets, produced using a combination of hydrogen decrepitation and milling, have been investigated. An isothermal anneal or a step anneal, both performed after homogenization, resulted in a marked improvement of magnetic properties of the sintered magnets. Thermomagnetic analysis (TMA) of the sintered magnets showed that, in addition to a matrix phase with a Tc = 314 ± 5 °C, there was another ferromagnetic phase with a Tc = 54 ± 5 °C. The microstructural investigations showed a considerable amount of free α-iron in the cast material, whereas no free iron was observed in the microstructure of the sintered magnets. However in very isolated areas within the sintered magnets, a Nd-Fe phase with Fe/Nd∼8 was identified (probably Nd2Fe17-type phase). The observation of this phase was consistent with results of TMA and the possible role of this phase in coercivity behavior is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349928
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  • 3
    Electronic Resource
    Electronic Resource
    The hydrogen decrepitation behavior of alloys and magnets based on Nd16Fe76B8 (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4626-4628 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hydrogen decrepitation (HD) behaviors of various forms of the permanent magnet alloy Nd16Fe76B8 and stoichiometric composition Nd11.8Fe82.3B5.9 have been investigated to provide background information on the production of sintered magnets by the HD process. The influence of the initial microstructures of the alloys on the subsequent HD behavior has been examined. Thus the as-cast ingots, homogenized ingots, and sintered magnets have been exposed to hydrogen at 2 bars of pressure at room temperature and the hydrogen absorption behaviors investigated by differential thermal analysis. The morphologies of the HD powders have been studied by scanning electron microscopy and have been related to the initial microstructures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344835
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  • 4
    Electronic Resource
    Electronic Resource
    Controlled solidification and magnetic properties of Pr-Fe-B-Cu and Nd-Fe-B alloys : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6104-6106 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The as-cast microstructure of the alloys Pr20.5Fe73.8B3.7Cu2 and Nd16Fe76B8 have been modified using a vertical floating-zone (VFZ) technique. By annealing the as-cast alloys and VFZ material at 1000 °C, the magnetic properties increased substantially for Pr-Fe-B-Cu alloy. VFZ growth rates up to 38 cm/h have not been sufficient to reproduce the as-cast ingot microstructure of the Pr-Fe-B-Cu alloy. Cast magnets prepared in a very small chill mold showed the best magnetic properties, with a (BH)max=98 kJ/m3. Sintered magnets prepared using the hydrogen decrepitation process from the large grained Nd-Fe-B zoned alloys exhibit inferior squareness factors to those prepared from the as-cast ingot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350060
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of aging at 500 °C on Nb-containing Nd-Fe-B magnets : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6606-6608 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The aging behaviors of Nd16.4Fe75.7B7.9, Nd16Fe76.3Nb0.3B7.4, and Nd14.5Dy1.5Fe76Nb1B7 magnets were investigated. The magnets were quenched and then aged at 500 °C to establish whether recovery of coercivity was possible below the melting point of the grain boundary. The samples were cooled and measured magnetically after 10- or 20-min intervals before being heated again for another interval. After aging at 500 °C for 55 min there was a dramatic increase in coercivity in the Nd-Dy-Fe-Nb-B samples, whereas the coercivity of the Nd-Fe-B samples remained unaltered. The results from thermomagnetic analysis on Nd-Dy-Fe-Nb-B show that an extra ferromagnetic phase is present in the magnets that had been aged for over 55 min and in the magnets that had full magnetic properties, but not in the quenched magnets. The Nd-Fe-B samples did not show any additional ferromagnetic phase. The experiments were repeated with Nd-Fe-Nb-B magnets and the results followed the same trend to those observed in the Nd-Dy-Fe-Nb-B magnets. The difference in coercivity between the aged and the initial-state magnets, for all types, was recovered upon heating at 650 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349872
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  • 6
    Electronic Resource
    Electronic Resource
    The production of high coercivity cast magnets using the HDD process : 35TH ANNUAL CONFERENCE ON MAGNETISM AND MAGNETIC MATERIALS San Diego, California (USA) 29 Oct−1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5838-5840 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nd-Fe-B as-cast alloys in the form of small ingots 4–5 mm thick and with composition Nd2.1Fe14B were transformed into high coercivity magnets using the hydrogenation disproportionation desorption (HDD) process without decrepitation of the blocks taking place. Magnetic measurements revealed that it was possible to produce blocks with coercivity of ∼780 kA m−1, remanence of ∼680 mT and a BHmax of ∼68 kJ m−3 (8.6 MGOe). The high coercivities in these samples were attributed to the disproportionation and subsequent recrystallization process. SEM metallographs of the samples processed at optimum temperature revealed an absence of the original large (∼200 μm) grains of Nd2Fe14B containing areas of free iron; instead an extremely fine grained, submicron, microstructure of single phase Nd2Fe14B grains was observed. In samples processed at temperatures higher than that found to be the optimum, larger Nd2Fe14B grains with extremely rectangular morphologies could be observed growing from surrounding submicron matrix grains. Domain patterns observed on these larger grains, using the Kerr effect, indicated that Nd2Fe14B matrix grains appear to grow predominantly with rectangular morphologies from the disproportionated material with the a and c crystal axis running parallel to the edges of the rectangle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347843
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic and mechanical properties of rotary forged aluminum compacted Nd-Fe-B magnets (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4622-4624 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and mechanical properties have been studied and compared for rotary forged aluminum compacts containing MQI and MQIII (isotropic and anisotropic melt-spun Nd-Fe-B, respectively) in the as-forged condition, and after subsequent heat treatment both above and below the Curie point. A maximum coercivity of 1165 kA m−1 and a maximum energy product of 84 kJ m−3 have been measured for compacts containing MQI material and 10% aluminum by volume. Compacts containing MQIII material possess superior fracture strengths to those containing MQI material in both bend tests (30 compared with 17 MPa) and uniaxial compression tests (185 compared with 67 MPa), and this is attributed primarily to more uniform compaction due to the morphology of the MQIII particles. Energy dispersive spectrography and fractography have indicated failure of MQIII compacts along interfaces between the aluminum and magnetic material, whereas MQI compacts fail through areas of incomplete compaction. In addition, heat treatment in vacuum subsequent to forging is shown to strengthen compacts containing both MQI and MQIII material substantially with only minor reductions measured in magnetic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344832
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  • 8
    Electronic Resource
    Electronic Resource
    Metal bonded Sm2Fe17N3−δ magnets (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6735-6737 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sm2Fe17N3−δ is a promising permanent magnet material but disproportionation above 650 °C means that only low-temperature processing can be considered. Sintering micron-size Sm2Fe17N3−δ powder with the soft, low-melting metals Zn, Bi, Sn, and Al has been investigated. Good results are obtained with zinc. A coercivity of 0.6 T and a maximum energy product of 84 kJ/m3 (10.5 MGOe) have been obtained. Zn7Fe3 is formed as a secondary phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348900
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  • 9
    Electronic Resource
    Electronic Resource
    Study of Sm(Co,Fe,Cu,Zr)7.1 magnets produced using a combination of hydrogen decrepitation and ball milling : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5856-5858 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of Sm(Co,Fe,Cu,Zr)7.1 sintered magnets produced using a combination of hydrogen decrepitation (HD) and ball milling have been investigated. The powder for the sintered magnets was produced by exposing the as-cast material to hydrogen at a slightly elevated temperature and then ball milling the friable material which resulted from the HD treatment. It was found that the combination of HD and milling is an effective means of production of 2:17 type sintered magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347847
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  • 10
    Electronic Resource
    Electronic Resource
    Microstructural and magnetic studies on Pr-Fe-B-Cu alloys : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6357-6359 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study on the microstructure and magnetic properties of alloys Pr20.5Fe74.0B3.5Cu2.0(A) and Pr17.0Fe76.5B5.0Cu1.5(B) has been carried out as a precursor to a study of the effects of high-temperature mechanical deformation on these materials. In the cast condition, the microstructure of alloy A consisted of three phases in the cast condition: Pr2Fe14B matrix phase, Pr-rich grain-boundary phase, and free Fe inside the matrix phase. The microstructure of alloy B in the cast state consisted of four phases: the same three phases as those observed in alloy A together with the PrFe4B4 phase. On annealing alloy A, an extra phase with needlelike or irregular form was observed in the grain-boundary regions. EDX (energy dispersive x-ray spectrometer)/WDX (wavelength dispersive x-ray spectrometer) analysis indicated that this phase is the Pr(Fe0.94Cu0.06)2 phase. In alloy B, the microstructures were not altered radically by annealing at high temperature except for the disappearance of the free iron. Alloy A exhibited much better permanent magnetic properties than those of alloy B, and this was attributed to grain size and improved magnetic isolation of the individual grains. The effects of low-temperature annealing on the magnetic properties at 500 °C have also been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349941
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