Die manuelle Auswertung von Laue-Aufnahmen mittels der stereographischen Projektion im Wulffschen Netz stößt bei hochindizierten Orientierungen auf erhebliche Schwierigkeiten. Es wird eine einfache Kugelmethode beschrieben, die es gestattet, mit Hilfe des Greeninger Netzes jedes beliebig orientierte Lauebeugungsdiagramm in kurzer Zeit auszuwerten.

Techn. Universiẗat, Diss., 2007--Darmstadt.

Experimental micromechanics of materials is a branch of science that seeks to build tight connections between composition, structure, processing and performance of materials under specific operating conditions required for particular technology applications. The present project is focused on the development of techniques that use the combination of electron, ion and X-ray microscopies to study the deformation behaviour of a particularly important class of metallic alloys used in the manufacture of aeroengines, namely, the so-called Ni-base superalloys. The complex hierarchical structure of these materials means that their macroscopic response is controlled to a great extent by the phenomena that play out on very fine scales, from angstroms (lattice spacing dimension) to nanometres (precipitates, phase boundaries, dislocations, chemical inhomogeneities) to microns (grains and their boundaries, defects and their clusters, dislocation pileups) to millimetres (component scale). Understanding the fine structure and deformation behaviour requires the development of specially configured experimental setup that allow the observation and quantification of deformation to external loading. In this study, FIB-SEM methods for sample characterization and fabrication were combined with synchrotron-based X-ray diffraction and imaging techniques, and backed up by theoretical analysis and numerical simulation, to elucidate the origins of the strength of these alloys. Micropillar compression tests using in-SEM nanoindentation were used to reveal the size dependence of the apparent strength, and connection was made with the dislocation-mediated crystal slip to provide an explanation of the observed Hall-Petch type dependence with a modified Hall-Petch equation considering both intrinsic and extrinsic characteristic lengths introduced. X-ray scattering was used in the polychromatic micro-Laue mode and using Bragg coherent diffractive imaging to reveal the crystal distortion arising due to plastic deformation. A Discrete dislocation dynamics in the 2.5D formulation was used to obtain a model description of the observed phenomena. The key outcome of the work presented in this thesis lies in the successful development of advanced observational tools and relevant theoretical or computational models for mesoscale plasticity problems for crystal with complex microstructure.

Die manuelle Auswertung von Laue-Aufnahmen mittels der stereographischen Projektion im Wulffschen Netz stößt bei hochindizierten Orientierungen auf erhebliche Schwierigkeiten. Es wird eine einfache Kugelmethode beschrieben, die es gestattet, mit Hilfe des Greeninger Netzes jedes beliebig orientierte Lauebeugungsdiagramm in kurzer Zeit auszuwerten.

No description available.

The semiconductor industry has decreased silicon-based device feature sizes dramatically over the last two decades for improved performance. However, current technology has approached the limit of achievable enhancement via this method. Therefore, other techniques, including introducing stress into the silicon structure, are being used to further advance device performance. While these methods produce successful results, there is not a proven reliable method for stress and strain measurements on the nanometer scale characteristic of these devices. The ability to correlate local strain values with processing parameters and device performance would allow for more rapid improvements and better process control. In this research, x-ray diffraction and convergent beam electron diffraction have been utilized to quantify the strain behavior of simple and complex strained silicon-based systems. While the stress relaxation caused by thinning of the strained structures to electron transparency complicates these measurements, it has been quantified and shows reasonable agreement with expected values. The relaxation values have been incorporated into the strain determination from relative shifts in the higher order Laue zone lines visible in convergent beam electron diffraction patterns. The local strain values determined using three incident electron beam directions with different degrees of tilt relative to the device structure have been compared and exhibit excellent agreement.

Complex concentrated alloys (CCAs) offer the unique ability to tune composition and microstructure to achieve a wide range of mechanical performance. Recently, the development of metastable CCAs has led to the creation of transformation-induced plasticity (TRIP) CCAs. Similar to TRIP steels, TRIP CCAs are more effective at absorbing high strain rate loads when TRIP is activated during the loading process. The objective of our study is to investigate the effect of copper on the critical pressure for activating TRIP and the high pressure stability of a Fe(40-X)Mn20Cr15Co20Si5CuX TRIP CCA, where x varies from 0 to 3 at.% Cu. To achieve this goal, diamond anvil cell testing during in-situ synchrotron radiation X-ray diffraction was performed using both a monochromatic wide angle X-ray scattering (WAXS) beam and, for the first time ever, a polychromatic Laue diffraction beam on a CCA. Laue diffraction allows for real-time phase evolution tracking of the γ-fcc → ε-hcp transformation in a high pressure environment. Based on the results, a new method for processing and preparation of high pressure samples without changing the microstructure of sample was developed. This new method can be used to prepare any CCA samples for high pressure testing.

Measuring atomic displacement inside crystals has been an important field of interest for decades especially in semiconductor industry for its effect on the crystal structure and symmetry, subsequently on the bandgap structure. There are three different image based, diffraction based, and electron holography based techniques using transmission electron microscope (TEM). These methods enable measuring atomic displacement inside specimen. However, among all TEM techniques offering nano-scale resolution measurements, convergent beam electron diffraction (CBED) patterns show the highest sensitivity to the atomic displacement. Higher order Laue zone (HOLZ) lines split by small variations of lattice constant allowing the atomic displacement measurement through the crystal. However it is a cumbersome measurement and it can only reveal the atomic displacement in two dimensions. Therefore, the atomic displacement information at each depth through the specimen thickness is still missing. This information can be obtained by recovering the phase information across the split HOLZ line. The phase profile across the split HOLZ line can be retrieved by the electron interferometry method. The phase of the diffracted beam is the required information to reconstruct the atomic displacement profile through the specimen thickness. In this work, we first propose a novel technique of self-interference of split HOLZ line based on the diffracted beam interferometry which recovers the phase information across the split HOLZ line. The experimental details of the technique have been examined to report the parameters in order to implement the method. Regarding the novelty of the technique and the lack of the of a reference phase profile to discuss the results, phase profile simulation was a main contribution. For simulating the phase profile across the split HOLZ line the Howie-Whelan formula supporting the kinematical theory of diffraction is used. Accordingly, the analytical approach to simulate the phase profiles across the split HOLZ line for three various suggested atomic displacements are studied. Also, the effect of some parameters such as the atomic displacement amplitude, the specimen thickness, and the g reflection is investigated on the phase profile. This study leads to an equation used for fitting the experimental results with the simulated phase profile. Consequently, self-interference of split HOLZ line (SIS-HOLZ) is studied as a method of reconstructing the phase profile across the split HOLZ line which carries the information of atomic displacement through the specimen thickness. / Graduate / 0548 / 0794 / mananrp@uvic.ca

No description available.

Microscopic beams of penetrating synchrotron radiation provide a unique tool for the analysis of material structure and deformation. This thesis describes my contributions to the development of new synchrotron X-ray micro-beam diffraction experimental techniques and data interpretation, and the use of experimental results for the validation of material deformation models. To study deeply buried material volumes in thick samples, the micro-beam Laue technique was extended to higher photon energies. Through-thickness resolution was achieved either by a wire scanning approach similar to Differential Aperture X-ray Microscopy (DAXM), or by applying tomographic reconstruction principles to grain-specific Laue pattern intensity. Both techniques gave promising first results. For reliable micro-beam Laue diffraction measurements of elastic strains in individual grains of a polycrystal, understanding of the error sources is vital. A novel simulation-based error analysis framework allowed the assessment of individual contributions to the total measurement error. This provides a rational basis for the further improvement of experimental setups. For direct comparison of experimental measurements and dislocation dynamics simulations, diffraction post-processing of dislocation models in two and three dimensions was developed. Simulated diffraction patterns of two-dimensional dislocation cell/wall type structures captured correctly some of the features observed experimentally in reciprocal space maps of a large-grained, lightly deformed aluminium alloy sample. Crystal lattice rotations computed from three-dimensional dislocation dynamics simulations of a Frank-Read source showed anisotropic orientation spread similar to that observed in micro-beam Laue experiments. For the experimental study of crystal lattice distortion, a novel technique was proposed that combines micro-beam Laue diffraction with scanning white-beam topography. Diffraction topography allows the study of lattice rotation at scales smaller than the scanning beam size. The new technique makes it possible to apply classical topography methods to deformed samples.