Rare earth-cobalt system permanent magnetic alloys and method of preparing same

Abstract

Permanent magnetic alloys comprising 11.5-12.5% rare earth components of which 6.3-12% is samarium and 0.5-6.2% is yttrium; 0.2-2.5% hafnium, .[.19.5-26.5%.]. .Iadd.10.5-26.5% .Iaddend.iron, 7-10.5% copper, and 52-70.7% cobalt, the ranges of the components being in atomic ratios. The alloys are prepared by obtaining 1-50 μm. powders of the components, compacting the powder after mangetic field orientation sintering the compacted powders at 1160°-1220° for 1-10 hours, cooling the sintered body at a rate of at least 1° C./second until the temperature is about 900° C., and then annealing the body at 750°-900° C.

What is claimed is: 
     
       1. Permanent magnetic alloys comprising 11.5-12.5% rare earth components of which 6.3-12% is samarium and 0.5-6.2% in yttrium; 0.2-2.5% hafnium, .[.19.5-26.5%.]. .Iadd.10.5-26.5% .Iaddend.iron, 7-10.5% copper, and 52-.[.70.7%.]. .Iadd.70.8% .Iaddend.cobalt, the ranges of the aforesaid components being in atomic ratios. 
     
     
       2. A method of preparing the alloys of claim 1 comprising the steps of melting raw material containing said components, solidifying the resulting melt, pulverizing the resulting ingot into powders having a grain size of 1-50 μm, compacting the powders after magnetic field orientation thereof, sintering said compacted powders at 1160°-1220° C. for 1-10 hours, cooling the sintered body at a rate of at least 1° C./second at least until the temperature is about 900° C., and then annealing the resulting bulk at 750°-900° C. 
     
     
       3. The method as in claim 2 where said annealing occurs at about 850° C. for about 1/2 hour. 
     
     
       4. The method as in claim 2 where said melting is effected in an inert atmosphere with a high frequency induction furnace or an electric arc furnace. 
     
     
       5. The method as in claims 2 or 4 where said cooling is effected by quenching the sintered body. 
     
     
       6. The method as in claim 2 where said grain size of the powders is 1-5 μm. 
     
     
       7. The method as in claim 2 where the sintered body is cooled to room temperature.