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After a general presentation of the beamline, specifically the workflow for ex-situ CT at BAMline is presented. Although being used in a broad variety of research fields the usual workflow for CT experiments is in most cases similar in terms of sample mounting, tomographic scan and reconstruction. Specific scanning schemes allow for a preview reconstruction carried out during the scan. A detailed description of the used hardware as well as the self-coded programs applied in the data pipeline will be given. This will be accompanied by a practical demonstration of the software involved in the entire process.
In order to investigate their microcracking behaviour, the microstructures of several β-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics.
X-ray refraction is an excellent tool for the characterization of the microstructure of materials. However, there are only a few (synchrotron) laboratories in the world that use this technique for material characterisation. Therefore, the seminar will first explain the basic principles of X-ray refraction and the measurement techniques installed at the hard X-ray beamline BAMline at BESSY II (Berlin, Germany). This is followed by examples of investigations on fibre-reinforced plastic composites (CFRP) as well as ceramic (Cordierite, ZrO2-SiO2) and metallic materials (Ti-6Al-4V, Inconel). Some of the investigations were carried out both ex-situ and in-situ under mechanical and thermal load. The results are correlated with the mechanical properties of the materials.
Synchrotron X-ray computed tomography (SXCT) at BAMline has been paired with in-situ tensile loading to monitor damage evolution in LPBF Metal Matrix Composite (MMC) 7017 Aluminium alloy + 3 wt% Zr + 0.5 wt% TiC. The processing of the material leads formation to different categories of Zr-rich inclusions, precipitates and defects. In-situ SXCT test disclosed the critical role of the pre-cracks in the reinforcement phases in the failure mechanisms of LPBF MMC. The damage was initiated from lack-of-fusion defects and cracks propagated through coalescence with other defects.
A recent upgrade of key equipment of the BAMline widens its imaging capabilities: shorter scan acquisition times are now possible, in situ and operando studies can now be routinely performed, and different energy spectra can easily be set up. In fact, the upgraded double-multilayer monochromator brings full flexibility by yielding different energy spectra to optimize flux and energy resolution as desired.
Synchrotron X-Ray computed tomography at the BAMline is constantly evolving. During monochromatic tomographic scans a preview reconstruction is offered. Newly introduced scanning schemes suppress certain types of reconstruction artifacts. Additionally, the application of a pink beam enables for faster tomographic scans even within seconds.
After a general presentation of the beamline, specifically the workflow for ex-situ CT at BAMline is presented. Although being used in a broad variety of research fields the usual workflow for CT experiments is in most cases similar in terms of sample mounting, tomographic scan and reconstruction. Specific scanning schemes allow for a preview reconstruction carried out during the scan. A detailed description of the used hardware as well as the self-coded programs applied in the data pipeline will be given. This will be accompanied by a practical demonstration of the software involved in the entire process.
The BAMline at the synchrotron X-ray source BESSY II (Berlin, Germany) is supporting researchers in a wide range of research areas since more than 20 years. These fields include biology, cultural heritage, medicine, and also materials science. As a non-destructive characterization method, synchrotron X-ray imaging, especially tomography with hard X-Rays, plays an important role in structural 3D characterization. A recent upgrade of key equipment at the BAMline expands the imaging capabilities towards shorter acquisition times. Therefore, in-situ and operando experiments can now be routinely conducted. Also, different energy resolutions can be set up to optimize flux and energy resolution as desired. This requires an adaptation of the used reconstruction methods in order to perform necessary analyses also during the experiment. In this presentation the equipment, data handling pipeline as well as various examples from material science are presented.
The BAMline at the 3rd generation synchrotron X-ray source BESSY II has been supporting researchers in a wide range of research areas for over 20 years. In addition to materials science, these fields also include biology, cultural heritage, and medicine. Being a non-destructive characterization method, synchrotron X-ray imaging, in particular tomography (SXCT), plays a particularly important role in structural characterization. A recent upgrade of key BAMline equipment expands the imaging capabilities: The upgraded dual multilayer monochromator offers flexibility by providing different energy spectra to optimize flux and energy resolution as desired. Different spectra (8 – 60 keV with ΔE/E 0.01%, 1.5%, 4% and pink beam) can be selected. The upgraded detector (in white beam configuration, equipped with an sCMOS camera) allows the higher flux to be exploited with reduced readout times. Shorter tomographic acquisition times in the range of seconds are now possible. Hence, in-situ and operando examinations are routinely available. An integrated slip ring allows continuous rotation of the sample stage for ease of wiring. The pink beam option allows tomographic observation of processes occurring in the time domain of a few seconds with a resolution down to ~ 1 µm. Different scan methods, optimized for quality and speed are available and discussed. Examples of energy related materials from fuel cell and battery research are shown.
An optional end station allows refraction enhanced imaging (synchrotron X-Ray refraction radiography (SXRR) and tomography (SXRCT)). That includes an analyzer Si-crystal in Bragg alignment between sample and detector. This technique obtains sensitivity to smaller structures (cracks, pores) down to a few wavelengths, while obtaining field of view sizes in the range of several mm. Besides medicine (e.g., teeth explants), several applications are found in material science, like studies on diesel particulate filters, ceramics, additively manufactured (AM) alloys and metal matrix composites (MMC). The in-situ capabilities include mechanical load (tension and compression) and heating up to 1100°C. A case study, the microstructural evolution during heat treatment of an AM AlSi10Mg, will be shown.
Absorption edge tomography is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. The beamline BAM line at BESSY II, which is operated by the Federal Institute for Materials Research and Testing, can provide a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%. Together with the microtomography setup, this enables differential tomography sensitive to any element with N >= 24 (Cr) by using an appropriate K- or L-edge in this range. Here, a polymer filament embedding metal organic framework (MOF) was prepared and used for 3D printing. Absorption edge tomography at the copper K edge was employed to perform a non-destructive 3D characterization of the microstructure of the embedded MOF. Data fusion was then used to determine the size distribution of the embedded MOF.