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Strategies for efficient and reliable texture measurements have been explored using the Nanoscale Ordered Materials Diffractometer (NOMAD) at the Spallation Neutron Source located at Oak Ridge National Laboratory (ORNL). To test these strategies, the texture of an Al alloy was also investigated using another neutron diffraction instrument, a constant-wavelength neutron diffractometer (NRSF2) located at the High Flux Isotope Reactor, also at ORNL. Reasonable agreement was found across the two experimental methods, but differences in overall texture strength and the symmetry of some components were noted, depending on the data reduction and analysis method selected. On the basis of these results, potential improvements are identified which would enhance the texture measurement capability on NOMAD.

This study reports an angular diffraction peak shift that scales linearly with the neutron beam path length traveled through a diffracting sample. This shift was observed in the context of mapping the residual stress state of a large U-8 wt% Mo casting, as well as during complementary measurements on a smaller casting of the same material. If uncorrected, this peak shift implies a non-physical level of residual stress. A hypothesis for the origin of this shift is presented, based upon non-ideal focusing of the neutron monochromator in combination with changes to the wavelength distribution reaching the detector due to factors such as attenuation. The magnitude of the shift is observed to vary linearly with the width of the diffraction peak reaching the detector. Consideration of this shift will be important for strain measurements requiring long path lengths through samples with significant attenuation. This effect can probably be reduced by selecting smaller voxel slit widths.

The texture of recrystallized straight-rolled -uranium foils, a component in prospective irradiation target designs for medical isotope production, has been measured by neutron diffraction, as well as X-ray diffraction using both Cu and Mo sources. Variations in the penetration depth of neutron and X-ray radiation allow for determination of both the bulk and surface textures. The bulk -uranium foil texture is similar to the warm straight-rolled plate texture, with the addition of a notable splitting of the (001) poles along the transverse direction. The surface texture of the foils is similar to the bulk, with an additional (001) texture component that is oriented between the rolling and normal directions. Differences between the surface and bulk textures are expected to arise from shear forces during the rolling process and the influence that distinct strain histories have on subsequent texture evolution during recrystallization. research papers 860 J. R. Einhorn et al. Crystallographic texture of -uranium foils J. Appl. Cryst. (2017). 50, 859-865 research papers J. Appl. Cryst. (2017). 50, 859-865 J. R. Einhorn et al. Crystallographic texture of -uranium foils 863 Figure 6Pole figures from the calculated ODF of the -uranium foil surface texture measured using Mo K X-rays and the (002), {111} and {112} peaks.

Numerous methods for measuring and analyzing texture are explored and discussed. Traditional pole figure inversion methods are compared against more recent developments in quantitative texture analysis involving the Rietveld whole pattern refinement method. A modified equal area pole figure collection strategy is compared to the conventional equiangular method using laboratory X-ray diffraction (XRD). The two measurement strategies were found to yield qualitatively similar orientation distribution functions (ODF), and the former set takes about half the time to collect. However, the estimated texture was found to be strongly dependent on the ODF computation parameters used in MTEX. The texture evolution during compression of a high specific strength Mgbase alloy containing long period stacking order (LPSO) phase is studied using synchrotron XRD. The initial texture was found to be much sharper than previously published results, demonstrating the importance of using a "direct method" to compute the OD for this material. The evolution of the texture of the Mg and LPSO phases suggests that the deformation is accommodated almost entirely by twinning in the former case and by dislocation slip, elastic deformation, and possibly some twinning in the latter. The texture of α-uranium foils is measured via X-ray (both Cu-and Mo-K α radiation) and neutron diffraction, and the results are analyzed with MTEX and MAUD (Rietveld), respectively. The three radiation sources are found to yield slightly different results, based on probing different depths of the foils. Finally, the capability of measuring texture on the Neutron Residual Stress Mapping Facility (NRSF2) and Nanoscale Ordered Materials Diffractometer (NOMAD) instruments at the Oak Ridge National Laboratory (ORNL) is demonstrated by comparing measurements to those obtained via conventional XRD methods. Pole figure inversion in MTEX (for XRD and NRSF2) and Rietveld analysis in MAUD (for NOMAD) are employed for analysis, and the results are quantitatively compared. Reasonable agreement is found across all methods, and the differences between methods are attributed mostly to differences in the analysis procedure. The implications of slight variations in texture, as estimated by the various techniques, are explored through calculations of tensor properties * Note that if is the identity matrix, then and coincide.