Synthesis of amorphous Nd15Fe77B8 alloy powders by mechanical alloying

Elemental Nd, Fe and B powders were mechanically alloyed using a high-energy ball mill under an argon atmosphere. The change in the structure and the magnetic properties were examined. X-Ray diffraction and differential scanning calorimetry combined with transmission electron microscopic studies revealed that powders milled for 100 h were mainly in the amorphous state. The amorphization by mechanical alloying is attributed to the energy accumulated during the mechanical alloying. The thermal stability of the amorphous materials produced by mechanical alloying was comparable to that of the amorphous materials produced by rapid solidification processing. Heat treatment of the amorphous powders above the crystallization temperature resulted in the formation of ferromagnetic Nd2Fe14B phase and showed excellent hard magnetic properties, as is the case for the amorphous Nd-Fe-B materials produced by the rapid solidification processing.