On the structural features of rapidly quenched strips of an industrial alloy of the Fe-Si-B-Nb-Cu system and their influence on crystallization and magnetic properties

The structure of the near-surface layers of industrially produced rapidly quenched tapes of an iron-based alloy with a mass ratio of alloying elements Si:B:Nb:Cu equal to 6.5:1.1:4.1:1 did not change along the entire length on the contact side. However, on the free side of the tape, the X-ray analysis of the structure of the near-surface layers showed the presence of oscillations in the intensity of the crystalline phase (most likely the Fe3Si phase with the crystallographic type of structure D03). Moreover, the crystalline phase formation was associated with the surface effects, since the surface grinding to a depth of 2 μm on the free side led to the complete disappearance of the crystalline component. At the same time, on the free side of the tape, the X-ray analysis of the structure of the near-surface layers showed the presence of oscillations in the intensity of the crystalline phase. In accordance with the periodicity of changes in the proportion of the crystalline phase, the magnetic properties (coercive force, saturation magnetic induction) were studied. The crystallization process the alloy tapes was considered. The study of the thermal stability along the length of the rapidly quenched alloy tapes in the initial state by the DSC method showed that the samples with different crystallinity of the surface layers on the free side of the tape, selected with a periodicity of 10 m, crystallized in the same temperature ranges: the first stage of crystallization occured from 493 to 554 °C, and the second from 653 to 698 °C. Magnetic properties (coercive force, saturation magnetic induction) were studied in accordance with the periodicity of the change in the proportion of the crystalline phase.