Patent ID: 9418779
Filing Date: 2016-08-16
CPC Classification: B22F,C22C,H01F

Claim Text:
1. A process for preparing a high-purity α-MnBi magnetic alloy, comprising: melting manganese (Mn) metal and bismuth (Bi) metal together in a ratio that is greater in manganese (Mn) metal than in bismuth (Bi) metal to form an alloy comprising between about 40 wt % and about 50 wt % α-MnBi material and residual fractions of unreacted manganese (Mn) metal and unreacted bismuth (Bi) metal therein; heat treating the alloy in an oxygen-free gas atmosphere at a first temperature less than or equal to about 266° C. for a time up to about 8 hours sufficient to form at least about 60 wt % α-MnBi material therein and a second temperature between about 266° C. and about 358° C. for a time up to about 5 hours sufficient to form a quantity of β-MnBi material therein; cooling the alloy after heating at a rate between about 1° C. per minute to about 10° C. per minute to decompose the quantity of β-MnBi material therein to increase the quantity of α-MnBi material therein; milling the alloy to agglomerate unreacted manganese (Mn) metal and unreacted bismuth (Bi) metal together therein and to fracture the α-MnBi material therefrom; sieving the milled alloy to collect the fractured α-MnBi material as a powder comprised of particles thereof in a fraction separate from the agglomerated manganese (Mn) and bismuth (Bi) metals fraction; and heat treating the fractured α-MnBi material fraction in a vacuum at a temperature selected between about 250° C. and about 300° C. for a time sufficient to form the high-purity α-MnBi magnetic alloy comprising at least about 90 wt % α-MnBi material therein.