Thoughts about the optimum data acquisition geometry and time resolution of monochromatic beam x-ray diffraction microscopy experiments

International audienceSo far, 3D X-ray diffraction microscopy (3DXRD) and X-ray diffraction contrast tomography (DCT) experiments have typically been performed in forward scattering geometry, the detector intercepting diffraction cones up to limited opening angles below 30°. The extension of the current synchrotron–based methodology towards 3D orientation mapping of deformed microstructures with down to (sub-)micrometer spatial resolution will require a reduction of the pixel and hence sample size by one order of magnitude. This in turn relaxes the need for high energy beams and opens interesting possibilities for new acquisition geometries, taking advantage of improved spatial resolution and strain sensitivity at high diffraction angles. First results obtained in this acquisition geometry will be discussed and a comparison to polychromatic micro-diffraction experiments is drawn

THOUGHTS ABOUT THE OPTIMUM DATA ACQUISITION GEOMETRYAND TIME RESOLUTION OF MONOCHROMATIC BEAM X‐RAY DIFFRACTION MICROSCOPY EXPERIMENTS

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Characteristics of stress relaxation kinetics of La60Ni15Al25 bulk metallic glass

The 0 relaxation typically plays an important role in the plastic deformation of glassy materials. Compared with amorphous polymers, most of the metallic glasses do not show evident beta-relaxation based on mechanical spectroscopy. However, La60Ni15Al25 bulk metallic glass (BMG) exhibits a prominent beta relaxation process, which could be an ideal model alloy to investigate the correlation between the beta relaxation and mechanical behavior of metallic glasses. In this work, compressive properties and stress relaxation at high temperature (below glass transition temperature T-g) were studied. Stress relaxation of La60Ni15Al25 BMG was measured by uniaxial compressive tests and mechanical spectroscopy around both a and beta relaxation temperature domain. At higher temperatures and sufficiently low strain rate, the flow behavior of the La50Ni15Al25 BMG could be simulated by a master curve, showing that the behavior is independent of temperature, especially on the proximity of the beta relaxation process. Because the existence of the beta relaxation, a high value of the activation volume for the plastic deformation could be ascribed to the existence of a specific atomic arrangement in the La(60)Nt(15)Al(25) BMG. It is found that compressive stress relaxation kinetics parameter remains temperature independent below T-g. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved