Abstract
Elemental neodymium, iron, and boron powder mixtures were mechanically alloyed in argon, hydrogen and nitrogen atmospheres. The resultant powders and those annealed at various temperatures were examined by X-ray diffraction, optical microscopy, and vibrating sample magnetometer. It was found that these powder mixtures absorbed hydrogen and nitrogen during the mechanical alloying. Heat treatment of the mechanically alloyed powders prepared in hydrogen atmosphere resulted in desorption of hydrogen gas. The resultant powders consisted of Nd2Fe14B ferromagnetic crystallites and showed a high coercivity value. On the other hand, heat treatment of the mechanically alloyed powders prepared in nitrogen atmosphere did not result in desorption of nitrogen gas. The resultant powders consisted of iron and neodymium nitrides and showed a coercivity as low as that of the powder mixtures. The Nd-Fe-B powders prepared by mechanical alloying in hydrogen atmosphere were magnetically isotropic.
