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We describe and illustrate a forward modeling method for quantitatively reconstructing the geometry and orientation of microstructural features inside of bulk samples from high energy x-ray diffraction microscopy data. Data sets are comprised of CCD images of Bragg diffracted beams originating from individual grains in a thin planar section of sample. Our analysis approach first reduces the raw images to a binary data set in which peaks have been thresholded at a fraction of their height after noise reduction processing. We then use a computer simulation of the measurement and the sample microstructure to generate calculated diffraction patterns over the same range of sample orientations used in the experiment. The crystallographic orientation at each of an array of area elements in the sample space is adjusted to optimize overlap between experimental and simulated scattering. In the present verification exercise, data are collected at the Advanced Photon Source beamline 1-ID using microfocused 50keV x-rays. Our sample is a thin silicon wafer. By choosing the appropriate threshold fraction and convergence criteria, we are able to reconstruct to ≤ 10µm errors the sub-region of the silicon wafer that remains in the incident beam throughout the rotation range of the measurement. The standard deviation of area element orientations is ≈ 0.3 degrees. Our forward modeling approach offers a degree of noise immunity, is applicable to polycrystals and composite materials, and can be extended to include scattering rules appropriate for defected materials.

A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is veri®ed by comparing an electron microscopy map of the orientations on the 2.5 Â 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 mm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Á4 9 10 À4 .