Magnetic properties of compacted alloy Fe73.5Cu7 Nb3Si13.5B9 in amorphous and nanocrystalline state

Uniaxial cold and hot pressing and shock wave compaction are used to produce ring cores from amorphous Fe_73.5Cu₁Nb ₃Si_13.5B₉ powder and ribbon. The microstructure of the cores is checked by X-ray diffraction. No crystallization is found during compaction. The magnetic hysteresis loops of the cores are measured in as-compacted state and after various heat treatments. Coercive force H_c and permeability μ, are determined as a function of annealing temperature between 400 and 650°C. Annealing to produce a nanocrystalline state is found to improve magnetic properties considerably. The lowest H_c (about 10 A/m) and the highest μ (about 10⁵) found for a ribbon-compacted sample are close to those measured in the wound ribbon. The observed magnetic behavior of the samples compacted in different ways is explained on the basis of stress and creep-induced anisotropies