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The effects of the additions of Co, Zr on microstructure and magnetic properties were studied for hot-deformed (HD) nanocomposite Nd11.5Fe81.5-xNb1CoxB6 (x=0, 2, 4, 8) and Nd11.5Fe82.5-xZrxB6 (x=0, 1) magnets, respectively. The remanence of hot-pressed (HP) magnets increased with increasing Co content firstly, but decreased when Co content was more than 2 at. % for HD magnets. Also the intrinsic coercivity (Hci) and maximum energy product ((BH)m) of HD alloys increased firstly, and then decreased with further increasing Co content. The maximum (BH)m of 24 MGOe was obtained at 2 at.% Co addition. Zr addition can improve significantly the c-axis alignment and magnetic properties of HD nanocomposite magnets, and HD Nd11.5Fe81.5Zr1B6 magnet with 1.5 wt.% Zn addition showed enhanced properties with Hci of 7100 Oe and remanent magnetization (Mr) of 1.06 T. The alloys have the structure of plate-like grains, but there are still many coarse grains, which may result from the un-uniform composition in the alloy.

Anisotropic bulk nanocrystal Nd-lean Nd-Fe-B magnets were prepared by hot-pressing the mixture of Nd11.5Fe81.5Nb1B6 melt-spun ribbons and pure Zn powder and subsequent hot-deforming. The effects of deformation on the magnetic properties and microstructure were also studied. The magnetic properties increased significantly for hot-deformed (HD) samples due to the formation of good c-axis texture with increasing deformation. The remanence Mr and maximal energy product (BH)m increased and reached their maximal values at 65% deformation due to the increasing orientation. On the other hand, the grains increased and were elongated normal to the press direction gradually with increasing deformation. The variation trend was similar to that of traditional Nd-Fe-B magnets. However, there was an obvious improvement for coercivity in the initial stage of hot-deformation resulting from the adequate Zn diffusion into grain-boundary. When the deformation was larger than 65%, the magnetic properties were deteriorated due to abnormal grain growth. In order to improve further the coercivity Hci, the samples with Dy addition were prepared. The coercivity of 12300 Oe could be obtained for anisotropic bulk Nd9.5Dy2Fe81.5Nb1B6.