High Performance Fe-Si-Al Magnetic Cores Made by Shock Wave Compaction

Fe-Si-Al powder cores were made by shock wave compaction in order to obtain high compacted density, and their electromagnetic properties were investigated. The compacted density with shock wave was higher than that compacted conventionally. The initial permeability and also the permeability under DC bias increased with increase of the green density. Demagnetizing factor of the core was estimated large compared to that of conventionally pressed core, and the reason is supposed that the longitudinal direction of the particle is orientated to the shock wave direction. On the other hand, the resistivity of compaction by shock wave was lower than that of conventional pressing. It is guessed that the surface insulator was broken by the shock wave. The eddy current loss decreased with increase of the resistivity, and over about 0.01Ωm it showed approximately constant. It is suggested that eddy current generates only inside the particle over about 0.01Ωm, however below the critical resistivity it runs inter-particle due to the contact between particles.