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Introduction and Pipelines
Published in Yongjie Jessica Zhang, Geometric Modeling and Mesh Generation from Scanned Images, 2018
There are many techniques and processes developed to create images, such as CT, MRI, nuclear medicine, ultrasound, and fluorescence for biomedical imaging. CT utilizes X-rays while MRI utilizes radio wave and magnetic field to scan objects. For both CT and MRI, the resulting images provide anatomy structure. Unlike CT and MRI, Nuclear Medicine injects radioactive source into the body, and then measures the radiation emitted from the body. The resulting images provide physiological functions of the object. Ultrasound utilizes high frequency sound waves in real time, generally 3~10 megahertz. Fluoroscopy uses a constant of X-rays, and it is also in real time. Cryo-EM (cryo-electron microscopy) is a popular scanning technique in structural biology to study small-scale objects like viruses at the level of Angstroms. In addition, people also scan metal materials. For example, electron backscatter diffraction (EBSD) is a microstructural-crystallographic technique used to examine the crystallographic orientation and elucidate texture or preferred orientation of polycrystalline materials. Instead of destroying the metal material like EBSD, high-energy X-ray is a nondestructive scanning technique to study polycrystalline materials. These various scanning techniques produce images for different types of objects. In some research areas like computer-aided design (CAD), people also use computational ways like signed distance function to compute volumetric imaging data. For biomolecules or proteins, people use the atomic resolution information to build electron density map and solve partial differential equations to obtain electron static potential distribution on regular grids.
Forward Modeling
Published in Jeffrey P. Simmons, Lawrence F. Drummy, Charles A. Bouman, Marc De Graef, Statistical Methods for Materials Science, 2019
In a polycrystalline material, the relevant microstructural entities are known as grains, i.e., regions of the material for which the crystal lattice has very nearly a constant orientation. Knowing the distribution of orientations is an essential prerequisite for the determination of material properties; if the properties of a single grain are known, then the bulk properties can often be approximated by averaging the single crystal property over the grain orientation distribution function (ODF). Electron backscatter diffraction (EBSD) has emerged as a leading technique for the determination of the ODF; EBSD is carried out in a scanning electron microscope (SEM), in which a fine electron probe with an energy of 20-30 keV is scanned across a region of interest and electron backscatter patterns are recorded on a scintillator screen. The experimental setup is shown schematically in Figure 4.2. The electron beam exits the objective lens pole piece and enters the sample surface at a given scan point; the goal of the measurement is to determine the orientation of the crystal lattice at this point. Electrons undergo both elastic and inelastic scattering events inside the material, and a fraction of the incident electrons emerges from the inclined sample as backscattered electrons (BSEs). A portion of those BSEs is intercepted by a scintillator screen at a distance L from the illuminated point; the light intensity pattern on the scintillator is then propagated along a fiber optic cable (or viewed by a lens) and recorded by a CCD camera. An example EBSD pattern is shown in Figure 4.2(b); this pattern was obtained for a silicon single crystal sample. The EBSD pattern shown in Figure 4.2(c) is a simulated pattern, using the forward modeling approach described in the remainder of this section.
The effect of severe plastic deformation and annealing conditions on mechanical properties and restoration phenomena in an ultrafine-grains Fe-28.5%Ni steel
Published in Philosophical Magazine, 2018
S. H. Mousavi Anijdan, H. R. Jafarian, N. Park
To perform microstructural analysis, the sheets were first mechanically polished. Then, a solution of 900 ml CH3COOH + 100 ml HClO4 at 11°C under 20 V was used for electro-polishing of the specimens. The evolution of the microstructure in the starting material and in the ARB-processed materials was studied by a field-emission type scanning electron microscope (SEM/Philips XL30S-FEG). The SEM instrument was equipped with an electron backscatter diffraction (EBSD) detector. TSL-OIM analysis software was also used to examine EBSD data of the starting material and also 1-cycle and 6-cycle ARB-processed specimens. High-angle grain boundaries (HAGBs) are defined as the boundaries having misorientation angle above 15°. And low-angle grain boundaries (LAGBs) are considered the boundaries having misorientation between 2° and 15°. Transverse direction section of the specimens was characterised for EBSD analyses. Grain-size measurement was performed by intercept method.
Effect of microwave hybrid heat treatment on the microstructure and hardness of 3D printed Inconel 718 superalloy
Published in Canadian Metallurgical Quarterly, 2023
Eslam M. Fayed, Vladimir Brailovski, Mohammad Jahazi, Mamoun Medraj
The microstructure and elemental distribution analysis of the as-printed and heat-treated samples were examined using a SEM (SU-8230 SEM Hitachi) equipped with an energy dispersive X-ray spectrometer, EDS. To this end, the as-printed and heat-treated samples were sectioned parallel to the printing direction using a slow diamond cutter (Buehler) with a mineral oil bath to prevent heat generation. The sectioned samples were gradually ground from 240 to 1200 grit using a waterproof SiC sandpaper, then polished down to 0.5 μm using an alcohol-based diamond suspension. Then, an automatic vibromet polisher was used to polish the samples down to 0.05 grit size using colloidal silica. A PANAnalytical X’pert Pro XRD with a CuKα radiation (45 kV and 35 mA) was used to analyse the phases and crystallographic texture evolution in the as-printed and heat-treated LPBF-IN718. An XRD scanning range (2θ) of 30–100° was selected to include the maximum number of diffraction peaks. All XRD spectra of the as-printed and heat-treated samples were scanned through the top surface perpendicular to the printing direction. The grain structure and crystallographic orientation of these conditions were analysed using an electron backscatter diffraction technique (EBSD, SU-8230 Hitachi SEM equipped with Bruker e-Flash HR+ EBSD detector). For the EBSD analysis, the specimens were ground and polished using the same procedures as for the SEM analysis. Then, an IM4000Plus Hitachi ion milling machine was utilised to remove residual scratches and deformed traces using a discharge voltage of 1.5 kV, an accelerating voltage of 6 kV and rotation speed of 25 rev min−1 for 40 min. For post-processing of the EBSD data, the Quantax Esprit [25] and ATEX [26] software were used.
Stacking fault aggregation during cooling composing FCC–HCP martensitic transformation revealed by in-situ electron channeling contrast imaging in an Fe-high Mn alloy
Published in Science and Technology of Advanced Materials, 2021
Motomichi Koyama, Misaki Seo, Keiichiro Nakafuji, Kaneaki Tsuzaki
After heating for reverse transformation, the specimen was mechanically polished with colloidal silica with a particle size of 60 nm. The polished specimen was set to a cooling stage (produced by the Mel-Build Corporation, Japan [23]) to conduct in situ ECCI during cooling from room temperature (20°C) to −51°C in the scanning electron microscope (Carl Zeiss Co., Ltd., Germany). The temperature was held within an accuracy of ±0.1°C for each observation. After the cooling experiment, the specimen surface was re-polished slightly with colloidal silica to remove contaminants such as hydrocarbons. Then, an electron backscatter diffraction (EBSD) measurement was carried out to identify the crystallographic orientation and phase. To investigate the reverse transformation as well, the same specimen was next set to a heating stage (produced by TSL Solutions, Japan [24]) for in situ ECCI. The specimen was heated from 20°C to 150°C in a microscope chamber. The acceleration voltage, probe current, and working distance for ECCI were set to 30 kV, 10 nA, and 3–4 mm, respectively. The EBSD measurement was carried out at 20 kV and 10 nA with a working distance of 15 mm. The beam step size was set to 50 nm. In the present observation, we first selected a grain where dark contrast appeared. The dark contrast in ECC images implies that the channeling condition is nearly satisfied. When the stacking fault and thin HCP martensite plate were characterized, the deviation parameter w [1,2] in the local region was confirmed to be positive by the EBSD measurement. Therefore, the present ECCI was not controlled [1] or accurate [25] ECCI in which the specimen inclination angle was determined based on the surface crystallographic orientation obtained prior to the operation of ECCI.