Amorphous bimetal ribbon of Fe78Si9B13 and (FeNiCr)78(SiB)22 was prepared with a double-chamber-crucible technique. Crystallization
temperature of the bimetal ribbon was examined by differential scanning calorimetry. The bimetal cores were annealed at 350℃ with longitudinal magnetic field. DSC curves of the bimetal are practically the superposition of those of the two components except a new exothermal peak of (FeNiCr)78(SiB)22 layer. Hysteresis loops of the annealed bimetal cores were measured. Although treated by field annealing, the bimetal cores are hard to be
magnetized, which is attributed to the internal stress caused by the cooling process after annealing because of the different thermal expansions of Fe78Si9B13 and (FeNiCr)78(SiB)22. At restrained state, the internal stress in the bimetal cores is calculated to be about 84 MPa. When the cores are relaxed from the bobbins, they will contract from the mean diameter of 27.5 mm to 18 mm. However, the stress iri the bimetal cores becomes more
complicated rather than released. The complicated stress in the relaxed bimetal cores makes them even more difficult to be magnetized.