Magnetic Properties and Substructure of Iron–Gallium Alloy Single Crystals Processed from Ingot to Wafers

Abstract

To process ingots of Fe–Ga alloy single crystals into wafers, Fe–17% Ga alloy crystals were cut using multi-wire sawing or electric discharging and rolling. Further, their properties of magnetization and magnetostriction were analyzed using electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). It was observed that the magnetization and magnetostriction curves changed with increasing rolling reduction. Although magnetization was negligibly affected by deformation, the shape of the magnetostriction curve of the as-grown crystal could be modified by a slight reduction in rolling or a slight plastic deformation. EBSD results show that rolling introduced dislocations to form heterogeneous dislocation cell walls and decreased the surface roughness of the wafers. The pole figures obtained by XRD indicate that the samples were single crystals; however, the crystal orientation was different from the ideal orientation after rolling. Residual stress measurements using the cos α method revealed that compressive and tensile stresses remained in the polycrystalline surface layers of the samples cut by multi-wire sawing and electric discharging, respectively. Moreover, the stresses were affected by the tensile strains or magnetic fields when the residual stresses were relatively small in the sample. Although the magnetization and magnetostriction of a single crystal are affected by rolling, they are not significantly reduced by small rolling reductions.

Fig. 5 Residual stresses for (a) sample B cut by multi-wire sawing and for (b) sample B with applied magnetic fields of 280 kA/m (displayed by stress ellipses). The magnetic field direction is in the x-axis or rolling direction.