Formation mechanism of stress-induced anisotropy in stress-annealed Fe-based nanocrystalline ribbon alloys

Abstract

The formation mechanism of stress-induced anisotropy in Fe73.5Cu1Nb3Si13.5B9 alloys is studied in-situ using synchrotron radiation XRD. The evolution of the diffraction spectra during the nanocrystallization and relaxation annealing of the ribbon samples is shown. The results reveal that the stress-annealed sample possess a positive and larger structural anisotropy Δq compared to the insignificantly negative Δq in the sample annealed without stress. Macroscopic strain (ε) and microscopic strain (e) measurements reveal that the structural anisotropy of the stress-annealed sample is released after the annealing process as residual strain, which confirms the stress-induced anisotropy to be magnetoelastic in origin. Relaxation annealing of the stress-annealed sample reveals that the structural anisotropy (Δq), induced transverse magnetic anisotropy (Hk), and anisotropy energy (Ku) are significantly affected while the macroscopic strain is insignificantly affected. We have then suggested the origin of stress-induced anisotropy can be attributed to magnetoelastic effects due to residual strains.