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

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).