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Several analyses are conducted to explain the microstructural changes of the Nd-rich phases taking place in the Nd-Fe-B sintered magnet during the postsintering annealing process. The reduction in the lattice mismatch is shown to be the main factor that leads to an enhancement of the magnetic properties of the compounds.

The article presents a new approach, which employs the melt spinning and jet milling techniques for the preparation of high performance nanostructured Nd-Fe-B fine powders. The different effects of the jet milling conditions on the particle size and magnetic properties of these powders are also studied.

The synthesis of [Nd.sub.25][Fe.sub.40][Co.sub.20][Al.sub.10][B.sub.5] by high-energy milling and melt-spinning techniques followed by subsequently annealed temperature range from 400 to 1100 degree Celsius for 20 min, is described. The findings from x-ray diffraction combined with high-resolution transmission microscopy for the annealed samples showed the presence of ferromagnetic [Nd.sub.2][(Fe,Co,Al).sub.14]B crystallites coexisting with antiferromagnetic [Nd.sub.6][(Fe,Co,Al).sub.14] ones, among an amorphous matrix.

Neutron diffraction patterns are acquired in situ from a melt-spun amorphous [Fe.sub.74][Nd.sub.5][B.sub.18][Cr.sub.3] alloy upon rapid thermal annealing at constant rates. The heterogeneous nucleation of [Nd.sub.2][Fe.sub.14]B on tetragonal-[Fe.sub.3]B precipitates promoted by the 3d transition-metal additives is used for magnetic hardening.

The pressure dependence of the growth of [alpha]-Fe and [Nd.sub.2][Fe.sub.14]B nanocrystals in amorphous [Nd.sub.9][Fe.sub.85][B.sub.6] is measured. The studies have shown that the growth of nanocrystals is dependent on atomic diffusion mediated by vacancy-type thermal defects.