CONTROLLED SOLIDIFICATION AND MAGNETIC-PROPERTIES OF PR-FE-B-CU AND ND-FE-B ALLOYS

The as-cast microstructure of the alloys Pr20.5Fe73.8B3.7Cu2 and Nd16Fe76B8 have been modified using a vertical floating-zone (VFZ) technique. By annealing the as-cast alloys and VFZ material at 1000-degrees-C, the magnetic properties increased substantially for Pr-Fe-B-Cu alloy. VFZ growth rates up to 38 cm/h have not been sufficient to reproduce the as-cast ingot microstructure of the Pr-Fe-B-Cu alloy. Cast magnets prepared in a very small chill mold showed the best magnetic properties, with a (BH)max = 98 kJ/m3. Sintered magnets prepared using the hydrogen decrepitation process from the large grained Nd-Fe-B zoned alloys exhibit inferior squareness factors to those prepared from the as-cast ingot.