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•Anisotropic Nd-Fe-B bonded magnets were obtained via Laser Powder Bed Fusion.•Mechanical orientation of elongated anisotropic magnetic particles was explored.•As-printed bonded ...magnets exhibited a mean alignment degree of < cos θ> = 0.73.•Alignment degree can be tailored as a function of the size of the magnetic particles.
Nd-Fe-B bonded magnets are an important class of permanent magnets, employed in many technological sectors. Additive Manufacturing (AM) enables the fabrication of net-shape bonded magnets with complex geometries, allowing to tailor their magnetic stray field specifically for a given application. A crucial challenge is the production of magnetically anisotropic components. Approaches presented in the literature up to now required a post-printing procedure or the complex integration of a magnetic field source into the AM process. Here, we present a technique to fabricate anisotropic bonded magnets via Laser Powder Bed Fusion (LPBF) by utilizing the mechanical alignment of anisotropic particles in a single step, without the need for a magnetic field source. Anisotropic bonded magnets were fabricated using a mixture of anisotropic Nd-Fe-B powder (MQA-38–14) and polyamide-12 (PA12). This magnetic powder consists of ellipsoidal particles, where the easy magnetization axis is distributed perpendicular to their longest side, and the mean aspect ratio of 3:1 can be exploited to generate magnetic texture. Depending on the particle size used as feedstock, the degree of alignment (<cosθ>) can be tailored to a maximum of <cosθ> = 0.78. The fabricated anisotropic bonded magnets exhibited a maximum remanence of Jr = 377 mT and an energy product of (BH)max = 28.6 kJ/m3, respectively.
The development of Additive Manufacturing (AM) of polymer bonded Nd-Fe-B magnets has focused on increasing remanence (Br) and maximum energy-product ((BH)max) values. One possible approach is to ...increase the volumetric fraction of magnetic particles on the as-printed components. The present contribution strives to shed light on how the combination of feedstock characteristics and process parameters can be critical factors to achieve such a goal in the case of the so-called Powder Bed Fusion (PBF) technique. In the present investigation, two feedstocks composed of polyamide-12 (Duraform PA2200, average particle size = 50 μm) and spherical Nd-Fe-B isotropic powder (MQP-S-9-8, average particle size = 35–55 μm), with different volumetric fractions of polyamide-12 (36 and 45 vol.%), were processed into magnet samples under three different laser speed values (LS = 600, 1000 and 1400 mm/s). The maximum geometrical density obtained of ρ = 4.33 g/cm3 was achieved for feedstock with 45 vol.% of polyamide-12 processed with LS = 600 mm/s, which represents 96% of the theoretical density for this composition. This combination resulted in remanence and maximum energy-product values of Br = 0.385 T and (BH)max = 24.1 kJ/m3, respectively. From SEM analysis, this combination promoted the formation of a continuous polymeric matrix, absent in the other explored condition, indicating that 36 vol.% of polyamide-12 or less is insufficient to encourage an adequate consolidation.
In this paper, the effect of the grain size on sintered Nd-Fe-B based permanent magnets was investigated. In order, the magnets were produced by different milling times at 200 rpm and then vacuum ...sintered at 1373 K for 60 minutes followed by cooling outside the furnace. The magnets either produced by lower and higher milling times (30 and 75 minutes) exhibited lower remanence and coercivity, due the inhomogeneous distribution of the grain sizes. The magnet produced by intermediary milling time (45 minutes) exhibited the highest properties among all samples, with remanence of 1.06 T, coercivity of 891.3 KA.m-1, maximum energy product of 211 KJ.m3 and a squareness factor equal 0.92.
The addition of alloying elements on rare-earth permanent magnets is one of the methods used to improve the magnetic properties. This present work evaluates the influence of alloying elements such as ...Zr, Nb and Mo on the microstructure and magnetic properties of sintered Pr-FeCo-B based permanent magnets. The permanent magnets were produced by the conventional powder metallurgy route using powder obtained by hydrogen-decrepitation (HD) method from as cast alloys. In order to produce the magnet Pr16Fe66,9Co10,7B5,7Cu0,7 without alloying elements the mixture of alloys method was employed, mixing two compositions: Pr20Fe73B5Cu2 (33% w.t) and Pr14Fe64Co16B6 (67% w.t). With the purpose of evaluating the influence of the alloying elements, the Pr14Fe64Co16B6X0,1 (where X= Zr, Nb or Mo) (67% w.t) alloy was employed. The characterization of the alloys and the magnets was carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS) and the magnetic properties were measured using a permeameter. The magnet without any additions presented the highest intrinsic coercivity (μ0iHc = 748 KA.m-1) while the magnet with Nb addition presented higher remanence (Br = 1,04 T). The magnet with Zr addition presented the highest maximum energy product (BHmáx = 144 KJ.m-3), and the magnet with Mo addition showed the highest squareness factor (SF = 0,73).
Active galactic nuclei: what’s in a name? Padovani, P.; Alexander, D. M.; Assef, R. J. ...
The Astronomy and astrophysics review,
11/2017, Letnik:
25, Številka:
1
Journal Article
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