Influence of various powder fabrication methods on magnetic properties of powder cores

Fe_78·4Si_9·5B₉Cu_0·6Nb_2·5 alloy powder cores were made from powders prepared by the pulverisation of crystallised ribbons, atomisation and high energy ball milling after atomisation. The results showed that the saturation magnetisation of the three powders showed negligible variation. The coercivity was found to be strongly affected by the microstructure of the powder. Cores made from pulverised powder exhibited the largest μ′ and core loss because of the small demagnetising field and large contact area caused by the flat shape of particles. In contrast, cores made from atomised powder exhibited the smallest μ′ and core loss because of the large demagnetising field and small contact area. Cores made from milled powder exhibited an intermediate μ' and core loss because of the change in powder shape caused by severe plastic deformation during ball milling.