Characterization of Residual Stress and Microstructure in a Functional Iron-Gallium Single Crystal Alloy

Abstract

X-ray diffraction (XRD) and scanning electron microscopy (SEM) in combination with electron backscatter diffraction (EBSD) were used to evaluate the residual stresses and microstructure of a functional Fe-Ga single crystal alloy. The single crystal was subjected to electrical discharge machining (EDM) and tensile deformation. A surface layer of polycrystalline grains was formed by EDM, and the residual stress of the single crystal was measured with the surface layer. The residual stresses in the surface layer revealed that the maximum principal stress of the alloy increased along the tensile direction during deformation, the results obtained by SEM-EBSD indicated that band-like microstructures corresponding to the {112}〈111〉 slip system were formed on the fracture surface after deformation. The observed traces of slip surfaces corresponded to deformation twins formed in the alloy. The results evaluated using XRD showed a correlation between the principal residual stresses and the microstructure observed by SEM-EBSD. The large principal stresses were found to be consistent with the direction of the applied tensile stress. Furthermore, the residual stresses were shown to change abruptly from tensile to compressive due to the shrinkage of the alloy at rupture. In addition, the residual stresses were shown to change abruptly from tensile to compressive due to the shrinkage of the alloy at rupture. These results indicate that stress measurements of single crystal alloys can be effectively performed by inducing polycrystals formed on the surface layer by EDM, and provide valuable insight into the stress distribution characteristics of such single crystal alloys due to deformation.