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  • 1
    Electronic Resource
    Electronic Resource
    Microstructure of hot-pressed and die-upset NdFeB magnets (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 967-971 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscopy was used to establish densification, alignment, and magnetization reversal mechanisms in hot-pressed and die-upset NdFeB magnets. Microstructures of these materials reveal two principal phases: Nd2Fe14B grains and a grain boundary phase of approximate composition Nd7Fe3. The grains in the hot-pressed material are polygonal and isotropic, while those in the die-upset material are flat platelets. The alignment of die-upset magnets arises exclusively from the fact that hot deformation produces platelets of Nd2Fe14B grains with their c axes parallel to the stress axis. It is argued that yielding plays an important role in the densification of the hot-pressed samples, and diffusion slip is critical to the alignment. The grain boundary phase appears as a crystalline or noncrystalline phase in the hot-pressed samples but has an fcc structure in the die-upset samples. Magnetic domain walls are shown to be pinned at the grain boundary phase in both cases. A Nd-rich spongy phase is observed to form at the boundaries where two ribbons fuse, but has no significance for the magnetic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339709
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of annealing on the microstructure of sintered Nd-Fe-B magnets (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2244-2246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A transmission electron microscopy study of sintered Nd-Fe-B magnets after annealing above 650 °C shows the formation of a thin intergranular Nd-rich layer extending to pockets of polycrystalline fcc Nd crystals. The grain boundary phase acts as a pinning site for the magnetic domain walls and is necessary for good magnetic hardening. On the other hand, the Nd1+εFe4B4 phase is an unavoidable product of the sintering process but need not be present for good coercivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336366
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  • 3
    Electronic Resource
    Electronic Resource
    Grain growth and alignment in hot deformed Nd-Fe-B magnets (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3528-3530 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of grain oriented Nd-Fe-B magnets from melt-spun ribbons by hot deformation has been studied using electron microscopy. It is shown that deformation and alignment of Nd2Fe14B magnets result from a combination of plastic deformation, grain boundary migration, and grain boundary sliding. Due to a limited number of available slip systems in this material, samples with large grains deform less easily. Small grain size materials, as encountered in the melt-spun ribbons, are well suited for die-upsetting to produce oriented magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340731
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  • 4
    Electronic Resource
    Electronic Resource
    Microstructure of hot-pressed and die-upset magnequench magnets (abstract) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3778-3778 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hot pressing is a convenient method for preparing fully dense Nd-Fe-B magnets from the melt-spun ribbons. Die-upsetting the hot-pressed material produces an aligned high-energy product magnet.1 Transmission electron microscopy was used to study the microstructures of both the hot-pressed and the die-upset magnets. For a starting composition of Nd14Fe81B5, it is found that the magnetic Nd2Fe14B phase comprises over 95% of the material. In the hot-pressed magnet, most of the Nd2Fe14B grains are nearly spherical and their distribution nearly isotropic, the average grain size around 100 nm. In contrast, the die-upset magnets consist of flat parallel grains with their c axes parallel to the stress axis. In the case of hot-pressed materials, a thin intergranular layer of an amorphous Nd-rich phase (like the one found in the melt-spun alloys)2 is seen. In the die-upset material, the flat surfaces between adjacent grains are free of any such intergranular phase. In both these magnets, 100–200 nm size noncrystalline particles with Nd/Fe over nine are found, their number and amount being an order of magnitude higher in the die-upset magnet. Also found are a crystalline phase of approximate composition Nd7Fe3 (boron content unknown) and an fcc crystal structure with lattice parameter 0.56 nm at the grain junctions. No Nd1+εFe4B4 phase is ever found in any of these samples. Lorentz electron microscopy indicates that the second and third phases act as pinning sites for the magnetic domain walls in these materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338968
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructure of high-remanence Nd-Fe-B alloys with low-rare-earth content : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6652-6654 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure and magnetic properties of bonded and fully dense magnets produced from melt-spun ribbons of the composition RE4.5TM76Ga1B18.5 have been investigated, where RE refers to a mixture of Nd and Dy, and TM refers to a mixture of Fe and Co. Results show that annealing overquenched ribbons with about 3 wt. % Dy and 3 wt. % Co at 700 °C can produce materials with Hci(approximately-equal-to)4 kOe, Br(approximately-equal-to)11.5 kG, and (BH)max(approximately-equal-to)14.5 MGOe, the latter being comparable to those of commercial ribbons containing three times as much Nd. The microstructure of annealed ribbons consists of about 30% Nd2Fe14B grains, 65% Fe3B grains, and 5% α-Fe grains. The grains of all the phases are nearly spherical. The grain diameters are in the 30–50 nm range. Hot-pressed magnets made from overquenched ribbons are fully isotropic, with magnetic and microstructural characteristics similar to those of the annealed ribbons. The high remanence and low coercivity correlate well with the microstructure consisting of a uniform mixture of the hard Nd2Fe14B phase and soft α-Fe and Fe3B phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356884
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  • 6
    Electronic Resource
    Electronic Resource
    The microstructure of hot formed neodymium–iron–boron magnets with energy product 48 MG Oe : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6470-6472 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Melt-spun Nd–Fe–B ribbons containing small amounts of Co, Ga, and C were die upset to 60% and 70% reduction in height in an argon atmosphere between 750 and 800 °C. The magnet, which was die upset 70%, has a remanence of 14.2 kG, Hci of 14.8 kOe, and (BH)max of 48 MG Oe. The interior of the magnet consists of well-aligned Nd2Fe14B grains separated by a Nd-rich intergranular phase. Intermixed with such aligned grains, we observed zones of unaligned fine-grained material without any intergranular phase. Since the intergranular phase is a key factor for deformation and alignment and it is uniformly distributed in the hot pressed precursor, it will be possible to enhance the alignment further by controlling the redistribution of the intergranular phase during die upsetting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352583
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  • 7
    Electronic Resource
    Electronic Resource
    Melt-spun Nd-Fe-B magnets and the Nd1+εFe4B4 phase (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5562-5564 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of Nd-Fe-B magnets made from melt-spun ribbons differs significantly from that of the sintered magnets. An ideal two-phase microstructure of small Nd2Fe14B grains surrounded by a Nd-rich intergranular phase is easily achieved in the melt-spun magnets while sintered magnets invariably contain the boron-rich Nd1.1Fe4B4 phase. This phase can form in the melt-spun alloys only when the cooling rates are slow and excess Nd and B are added deliberately. In those cases, this new phase appears as randomly distributed and randomly oriented grains of the same size as the Nd2Fe14B grains. The Nd1.1Fe4B4 grains are highly faulted in the Fe sublattice with their fault planes parallel to the (110) plane. Energy dispersive x-ray analysis and diffraction shows that this phase forms with varying Nd:Fe ratios in different grains. We have also found that the faults form in pure bulk samples of Nd1.1Fe4B4 but not in pure NdCo4B4 samples. Possible antiphase boundaries arising from modulated Fe sublattice are seen. The faulted microstructure is believed to result from (a) sluggish kinetics of formation of this phase, (b) incommensurate crystal structure, and (c) weak bonding between the Nd chains and chains of Fe-B tetrahedra that make up the structure. Lorentz microscopy shows this phase to act as a weak barrier to domain wall motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342308
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  • 8
    Electronic Resource
    Electronic Resource
    Enhancement of Ductility in Aluminum Alloys by the Control of Transition-Metal Solutes during Thermo-Mechanical Processing (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 475-479 (Jan. 2005), p. 421-424 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Predictions of chromium additions to aluminum alloys to stabilize the deformation debris products were examined. Additions of 0.22 wt. % Cr to AA6063 extrusion alloys manifested enhanced formability under bending and precision-strain-rate-sensitivity tensile testing indicated that the stacking fault energy was reduced. The debris products were more resistant to dynamic recovery resulting in enhanced ductility at 27 °C and the solute-drag effect of Mg was dramatically manifested in the Haasen plot
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/09/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.475-479.421.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Application of Microstructure Sensitive Design to FCC Polycrystals (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 546-549 (May 2007), p. 675-680 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Microstructure Sensitive Design (MSD) offers a rigorous mathematical framework forrepresenting the relevant statistical details of the material microstructure for a given design problem,and for developing quantitative invertible relationships between these microstructure representationsand the macroscale properties of interest. The methodology makes extensive use of Fourierrepresentations of the distribution functions representing the material internal structure and existinghomogenization theories. In this paper, we describe the application of the MSD framework to fccpolycrystals with a specific focus on the crystallographic texture as the microstructure designvariable. The advantages of the MSD approach are demonstrated through a number of elastic-plasticproperty closures for cubic metals
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.546-549.675.pdf
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  • 10
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    Electron microscopy of some rare earth–cobalt alloy magnets (1978)
    American Institute of Physics
    Details
    Publication Date: 1978-03-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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