MICROSTRUCTURAL STUDIES OF ND-FE-B POWDERS PRODUCED BY GAS ATOMIZATION

Nd15Fe77B8 powders (particles) were produced by helium and argon atomi zation at pressures ranging from 3 to 9 MPa. The average particle diam eter decreased with increasing atomizing pressure. The microstructures of the atomized powders were investigated under a scanning electron m icroscope. Except for the very fine powder (less than 2 mum), the micr ostructures were dendritic. The relationship between the particle diam eter and the grain size of the dendrites was linear. This result sugge sts that the grain size is dependent only upon the particle diameter, no matter how high the applied atomization pressure is, provided the c ooling medium (atomizing gas) is the same.