Author：Date：2019-7-30
Iron-based alloy materials are widely used in various fields due to their excellent soft magnetic properties. In order to meet the different needs of various fields, people regulate the structure and magnetic properties of materials. Common methods include magnetic field annealing and stress annealing. Stress annealing has certain advantages over magnetic field annealing. In 1992, Kraus et al. used stress annealing to treat Fe-based alloy ribbons, and the magnetic anisotropy was several times that of magnetic field annealing. Since then, stress annealing regulation magnetic structure technology has received extensive attention. But until now, there has been considerable controversy about the mechanism of magnetic anisotropy induced by stress annealing. Among them, the most representative ones are the magnetic-elastic coupling interaction model proposed by Herzer, and the direction-ordered model based on Néel atoms by Hofmann and Kronmüller. The latter proposes that in addition to the magnetoelastic coupling interactions considered by Herzer et al., the ordering of the Fe-Si atoms in the direction may also be the cause of the magnetic anisotropy. Later, Ohnuma et al. used transmission X-ray diffraction technology to directly observe the stress annealing caused by the lattice anisotropy of Fe-based alloys. It is claimed that lattice anisotropy is a direct evidence of induced magnetic anisotropy and that stress annealing is induced. The magnetic anisotropy can be completely eliminated by long or multiple isothermal tempering. The magnetic properties of nanocrystalline materials are closely related to its microstructure. Fang et al. studied the mesostructure of stress-annealed Fe-based alloy ribbons by atomic force microscopy. It is suggested that nanocrystalline orientation agglomeration is also stress annealing induced magnetic anisotropy. The important reason is that nanocrystalline directional agglomeration cannot be completely eliminated by isothermal tempering. This leads to a controversial question: Can the magnetic anisotropy induced by stress annealing in the Fe alloy ribbon be completely eliminated by tempering? The answer to this question is not only scientific but also important for production practice.
In this paper, the synchrotron radiation X-ray diffraction (XRD) technique was used to observe the changes of the microstructure of Fe-based alloy ribbons during multiple tempering. The relationship between microstructure, macroscopic strain and magnetic anisotropy and tempering frequency was compared. Analyze whether stress-induced annealing magnetic anisotropy can be completely eliminated by tempering.
(3) The magnetic anisotropy of the ribbon has a linear relationship with the lattice anisotropy, but the intercept of the inverse extension line and the ordinate of the relationship curve is not zero, and the lattice anisotropy is still zero. 16.36% magnetic anisotropy, which is different from the conclusion that Ohnuma et al. "lattice anisotropy is the direct cause of magnetic anisotropy";
(4) Although the lattice anisotropy caused by the residual stress in the stress annealing process is the main reason for the magnetic anisotropy, it is not the only reason, the nanocrystalline crystal caused by the creep plastic deformation part of the amorphous substrate during the stress annealing process. Particle orientation agglomeration is also an important reason for the magnetic anisotropy induced by stress annealing. Moreover, the magnetic anisotropy induced by the agglomeration of nanocrystalline crystallites due to the creep plastic deformation of the amorphous substrate during stress annealing cannot be used back. The fire method is completely eliminated.
