Warm consolidation of amorphous metallic powder composites for AC applications

Amorphous Co68.8Fe4.2Si15B12powders of zero magnetostriction were subjected to warm consolidation with resins for the purpose of AC applications. The amorphous compact of more than 90% of the packing fraction was obtained by consolidation utilizing viscous flow. The magnetic properties of the composite toroidal cores at high frequency range were evaluated by the frequency dependence of the permeability. It was certified that the liquid-state resins were more efficient on the electric isolation of the metallic particles to reduce eddy current losses than the powder resins which occupied the pores within the compact, preferentially. The polyimide varnish was, in particular, advantageous on such thermal resistance and thermosetting characteristics that enabled the denser compact at the temperature above the softening point of the amorphous alloy and the proper annealing for stress relaxation. The compact obtained with polyimide exhibited permeability higher and more stable against frequencies than the commercial iron dust core.