RAPID THERMAL ANNEALING OF 2-PHASE NANOCRYSTALLINE MAGNET ALLOYS

Nanocrystalline composite magnets consisting both of a magnetically ha rd phase and a magnetically soft phase show high saturation magnetizat ion, high remanence ratio and large coercivity. The nanostructure depe nds very much on the processing, treatment used, e.g., conventional ra pid annealing (CRA) or flash annealing. In this study, rapid thermal a nnealing (RTA), commonly used by IC industries, was adopted to anneal various melt-spun Nd-Fe-B flakes, and these flakes and compared to tho se obtained from CRA. It was found that for the alloys with a higher a lpha-Fe fraction, RTA is more capable of attaining, within a heating c ycle of less than 200 seconds, superior properties to those from CRA. High resolution TEM study showed that RTA leads to a finer and more un iform nanostructure than those obtained by CRA. The effect of composit ion on the magnetic properties of RTA treated alloys was also studied. It was concluded that the RTA process has potential for the mass prod uction of nanocomposite alloys.