Structural aspects of stress-induced magnetic anisotropy in Fe-based nanocrystalline alloy

Abstract

This work is focused on the quantitative description of structural anisotropy in the Fe73.6Cu1Nb3Si15.5B6.9 alloy induced in the process of nanocrystallization during tensile annealing. Structural changes induced by annealing under uniaxial tensile deformation were investigated using X-ray diffraction. It was shown that Fe3Si nanocrystalline grains growing in the tensile direction have a higher value of the lattice spacing. An opposite behavior is seen in transversal direction. The difference between the value of the lattice strain determined in the longitudinal and transverse directions is proportional to the magnitude of the tensile stress applied and represents a quantitative parameter determining the degree of stress induced anisotropy (SIA). Strain pole figure (SPF) measurements provide evidence that the SIA is uniaxial, and its main axis is aligned along tensile direction. Quantitative comparison of the SPFs shows that the strain partitioning among different Bragg reflections is not even and {400} family of planes exhibits the highest magnitude of the SIA. Furthermore, it was found that the magnitude of the SIA for a given set of Bragg reflections {hkl} is inversely proportional to its Young’s modulus Ehkl.