FE-ND-C-BASED INGOT PERMANENT-MAGNETS BY SOLID-STATE TRANSFORMATION

The effects of composition, annealing temperature, and annealing time on the magnetic properties and microstructure of Fe(66)M(2)Nd(20)C(9.5 )B(0.5) (M=Ga,Nb,Cu,Al) ingot magnets are presented. It has been found that the magnitude of the hard magnetic properties, which evolve duri ng the solid-state transformation Fe17Nd2Cx to Fe14Nd2C, depends on th e additive elements. These additions which decrease the melting temper ature of the intergranular phase accelerate the transformation process and those which increase this temperature retard the transformation. Coercivities up to 880 kA/m combined with a remanence 0.58 T were prod uced in alloy ingots with Cu. The initial grain size was found to be c rucial in producing good magnetic properties and coercivities as high as 980 kA/m were achieved for Fe-Nd-C-B alloy magnets hot pressed from microcrystalline melt spun ribbon. A modest increase of remanence (si milar to 0.7 T) was achieved by die-upset forging of ingot alloys.