In- situ Tensile Tester for Scanning Three-Dimensional X-ray Diffraction Microscopy

Understanding of deformation and degradation of bulk metals under loading is necessary to improve the safety and environmental performance of mechanical components such as automobile parts. One of the key parameters in mechanical characterization is strain. Large strains that affect reliability can often be measured as changes in the crystallographic orientation. Electron backscatter diffraction (EBSD) method can measure strains only on the sample surface. However, since strain distribution varies under constrained conditions, nondestructive measurement inside the material is necessary to determine the actual mechanical response of the material. We propose scanning three-dimensional x-ray diffraction microscopy, 3DXRD, in combination with the in- situ measurement tensile tester. High-energy synchrotron radiation x-ray enables internal measurements, and the diffraction method using scanning microbeam and conical slits enables measurement of threedimensional distributions. The development of a special in-situ loading device that can be used in the limited space of 3DXRD setup has realized measurement of deformation behavior of steel during the tensile loading process. This technique enabled the nondestructive measurement of crystallographic orientation change in 80 grains before and after plastic deformation. It was found that even when grains exhibited similar orientations before plastic deformation, it was not the case after plastic deformation. The magnitude of crystallographic orientation change due to tensile loading is considered to depend on local constraints such as the orientation, grain size, 3- dimensional position, and shape of adjacent grains. Nondestructive strain measurement techniques as shown here are considered important for the advancement of evaluation methods for deformation and deterioration of mechanical components.