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Effect of tungsten content on microstructure and magnetic properties of nanocomposite Nd10Fe84-xWxB6 (0

Przybył A., Wysłocki J. J., Leonowicz M., Kaszuwara W., Frąckowiak J.

Archives of Materials Science

2006

Vol. 27, nr 2-3

85-99

The investigation was carried out on nanocomposite Nd10Fe84-xWxB6 magnets with different tungsten content (from 0 to 33 at.%) produced by the mechanical alloying method. The alloys have a fine grained and highly porous structure. As tungsten is added the powder particles become progressively smaller and are distributed uniformly throughout the whole specimen volume. From the phase structure determination using X-ray diffraction, Moessbauer spectroscopy and transmission electron microscopy it has been found that with the increase of tungsten content in the magnets the amount of the magnetically hard Nd2Fe14B and the soft alpha-Fe phases decrease. Instead, paramagnetic phases appear. Moreover, the addition of tungsten to the basic composition results in a significant increase in coercivity jHc (from 260 to 1350 kA/m) and a reduction in both the remanence Br (from 0.95 to 0.24 T) and the maximum magnetic energy product (BH)max (from 80 to 13 kJ/cubic m).

Microstructure and magnetic properties of nanocrystalline Nd2Fe14B/alpha-Fe magnets with different grain size.

Wnuk I., Wysłocki J. J., Przybył A., Kaszuwara W., Leonowicz M.

Archives of Materials Science

2005

Vol. 26, nr 4

263-277

The nanocomposite Nd2Fe14B/alpha-Fe magnets with different grain size produced by mechanical alloying were studied. The phase composition of the magnets was determined on the basis of X-ray diffraction and Moessbauer spectroscopy. It was stated that the alloy is composed of three phases (with different volume fraction depending on the milling time): the magnetically hard phase Nd2Fe14B and the magnetically soft phases alpha-Fe and Nd2Fe17. In metallographic examinations, the techniques of optical, scanning and transmission electron microscopy were employed. Moreover, magnetic properties were determined depending on milling time (grain size). Maximum magnetic properties were achieved in the magnet produced from powders obtained after 90 hours' milling, which were as follows: Jr=0,914 T; jHc=251.1 kA/m; Js=2.12 T and (BH)max=67.7 kJ/cubic m.