Three-dimensional X-ray structural microscopy with submicrometre resolution

Abstract

Advanced materials and processing techniques are based largely on the generation and control of non-homogeneous microstructures, such as precipitates and grain boundaries. X-ray tomography can provide three-dimensional density and chemical distributions of such structures with submicrometre resolution; structural methods exist that give submicrometre resolution in two dimensions; and techniques are available for obtaining grain-centroid positions and grain-average strains in three dimensions. But non-destructive point-to-point three-dimensional structural probes have not hitherto been available for investigations at the critical mesoscopic length scales (tenths to hundreds of micrometres). As a result, investigations of three-dimensional mesoscale phenomena--such as grain growth, deformation, crumpling and strain-gradient effects--rely increasingly on computation and modelling without direct experimental input. Here we describe a three-dimensional X-ray microscopy technique that uses polychromatic synchrotron X-ray microbeams to probe local crystal structure, orientation and strain tensors with submicrometre spatial resolution. We demonstrate the utility of this approach with micrometre-resolution three-dimensional measurements of grain orientations and sizes in polycrystalline aluminium, and with micrometre depth-resolved measurements of elastic strain tensors in cylindrically bent silicon. This technique is applicable to single-crystal, polycrystalline, composite and functionally graded materials.

Critical issues in hydrogen assisted cracking of structural alloys

“…EBSD was applied to investigate local plasticity associated with cracking [63] and this technique should be exploited. Micro-Laue diffraction using focused synchrotron x-rays probes a material in 3 dimensions with spatial resolution of -0.5 x 0.5 x 1.0 gm [64]. For aluminum, the maximum probe depth is -75 gm.…”

Boundary migration during recrystallization: experimental observations

“…With this technique, 3D maps of orientations within both individual deformed and recrystallized grains with a spatial resolution of ~300 nm have been achieved [52]. The 3DXRM techniques utilize a focused, polychromatic synchrotron X-rays with energy of 5-30 keV [51,53]. A Pt wire is used as a differential aperture to differentiate diffraction signal from different sample depth along the beam, and crystallographic information is resolved by indexing the Laue diffraction patterns at each depth [51].…”

“…The 3DXRM techniques utilize a focused, polychromatic synchrotron X-rays with energy of 5-30 keV [51,53]. A Pt wire is used as a differential aperture to differentiate diffraction signal from different sample depth along the beam, and crystallographic information is resolved by indexing the Laue diffraction patterns at each depth [51]. Practically, due to limitations from the imperfection of the focusing mirror, the spatial resolution is ~500 nm.…”

“…[49,50]) and differential aperture X-ray microscopy techniques (also called 3D X-ray crystal microscopy (3DXRM)) (e.g. [51]). With these techniques, the boundary migration can be traced in situ/ex situ in 3D, so that full boundary information described by 5 parameters (3 for misorientation and 2 for boundary plane normal) can be obtained, and the influence of 3D deformed microstructure on boundary migration can be directly visualized.…”

Proceedings of the 13th World Conference on Titanium

“…Examples here are the differential aperture X-ray microscopy (DAXM) [16] and far-field 3D X-ray diffraction (3DXRD) [17]. X-ray DCT [18,19] is a variant of the 3DXRD microscopy technique enabling simultaneous reconstruction of the 3D microstructure (shape and orientation) in suitable polycrystalline materials, along with the absorption map of the specimen.…”