Effects of Nb addition and/or casting method on the amount of precipitated Fe in NdFeB alloys

A novel method has been developed to measure the amount of precipitated Fe in a series of (Nd/sub 0.9/Dy/sub 0.1/)/sub x/Fe/sub 93.5-x-y/Nb/sub y/B/sub 6.5/ alloys, where x=13, 14, 15, or 17, and y=0 or 0.5. It has been found that the amount of precipitated Fe decreases significantly with increasing rare earth content. Nb has been found to suppress the amount of precipitated Fe by approximately 50% for all compositions studied. Rapid solidification via an inert gas atomization process has been used to further suppress the amount of precipitated Fe in (Nd/sub 0.9/Dy/sub 0.1/)/sub x/Fe/sub 93-x/Nb/sub 0.5/B/sub 6.5/ where x=13 and 14. The amount of precipitated Fe can be efficiently decreased, overcoming the problems suggested by the equilibrium phase diagram for these alloys. It is concluded that inert gas atomization offers a promising means to produce alloy powders with fewer Fe-precipitates, and thus sintered magnets with superior magnetic properties and corrosion resistance.<
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