Differences in microstructure and magnetic properties between directly-quenched and optimally-annealed Nd-Fe-B nanocomposite materials

Melt-spun Nd9.5Fe81Zr3B6.5 ribbons were prepared by the single roller melt-spinning technique. The microstructure and magnetic properties of directly-quenched and optimally-annealed Nd-Fe-B nanocomposite materials were studied by X-ray diffraction, transmission electron microscopy observations, and magnetization measurements. The experimental results show that crystallizing an precursor into nanocrystallines is ineffective for obtaining better magnetic properties, while nanocomposites with excellent properties can be directly melt spinning at an optimum wheel speed. The microstructure of the ribbons at various distances from the ribbon wheel side was studied. It shows that in the inner part of the ribbons. the directly-quenched ribbons and optimally-annealed ribbons have similar characteristics of microstructure. However, in the free-surface and wheel-contacted surface the grain size of the annealed ribbons is much coarser than that of the directly quenched ribbons. (C) 2009 Elsevier B.V. All rights reserved.