AMORPHIZATION OF ND15FE77B8 ALLOY INGOTS BY MECHANICAL GRINDING

Amorphous powders of a Nd15Fe77B8 alloy were obtained by mechanical grinding of the alloy ingots. Mechanical grinding of Nd15Fe7B8 alloy ingots reduced the average particle size to 1 mum within the relatively short period of milling times. Extended milling did not yield further reduction in particle size, but resulted in a change in the structures from Nd2Fe14B crystallites to an amorphous structure. It was found that the crystallization of alpha-iron from amorphous matrix took place in some stage of milling. The amorphous materials were stable up to 820 K at a heating rate of 0.33 K/s. Heat treatment of the amorphous materials above the crystallization temperature resulted in the crystallization of the Nd2Fe14B phase and the resultant materials showed a high coercivity of 11.9 kOe as in the case for the amorphous Nd-Fe-B materials produced by rapid quenching techniques.