Modern analytical tools, from microfocus X-ray diffraction (XRD) to electron microscopy-based microtexture measurements, offer exciting possibilities of diffraction-based multiscale residual strain measurements. The different techniques differ in scale and resolution, but may also yield significantly different strain values. This study, for example, clearly established that high-resolution electron backscattered diffraction (HR-EBSD) and high-resolution transmission Kikuchi diffraction (HR-TKD) [sensitive to changes in interplanar angle (Δθθ)], provide quantitatively higher residual strains than micro-Laue XRD and transmission electron microscope (TEM) based precession electron diffraction (PED) [sensitive to changes in interplanar spacing (Δdd)]. Even after correcting key known factors affecting the accuracy of HR-EBSD strain measurements, a scaling factor of ∼1.57 (between HR-EBSD and micro-Laue) emerged. We have then conducted "virtual" experiments by systematically deforming an ideal lattice by either changing an interplanar angle (α) or a lattice parameter (a). The patterns were kinematically and dynamically simulated, and corresponding strains were measured by HR-EBSD. These strains showed consistently higher values for lattice(s) distorted by α, than those altered by a. The differences in strain measurements were further emphasized by mapping identical location with HR-TKD and TEM-PED. These measurements exhibited different spatial resolution, but when scaled (with ∼1.57) provided similar lattice distortions numerically.

Electron backscatter diffraction (EBSD) is an excellent tool for characterizing the crystallographic orientation aspects of the microstructure of polycrystalline material. In some additively manufactured materials, the material may undergo a phase transformation during the forming process. Although EBSD can only characterize the final microstructure, neighbor information from orientation mapping allows the microstructure before the phase transformation to be reconstructed, provided that the parent–child orientation relationship is known. An investigation of the effectiveness of the reconstruction algorithms for capturing the grain size as well as orientation gradients is undertaken with a focus on additively manufactured Ti-alloy. The EBSD results, coupled with reconstruction algorithms, reveal information on the prior grain size as well as the plastic flow of the material.

Introduced over ten years ago, cross-correlation-based electron backscatter diffraction has enabled high precision measurements of crystallographic rotations and elastic strain gradients at high spatial resolution. Since that time, there have been remarkable improvements in electron detector technology, including the advent of ultra-high speed detectors and the commercialization of direct detectors. In this study, we assess the efficacy of multiple generations of electron detectors for cross-correlation-based analysis using a single crystal Si sample as a reference. We show that, while improvements in precision are modest, there have been significant gains in the rate at which high-quality diffraction patterns can be collected. This has important implications in the size of datasets that can be collected and reduces the impact of drift and sample contamination.

The mechanical properties of additive and traditionally manufactured alloys are largely dependent on the characteristics and distribution of dislocation cell networks that develop during the fabrication process. This work demonstrates the ability to quantitatively characterize these dislocation structures by high angular resolution electron backscatter diffraction analysis using a direct electron detector. The defect structures are characterized in terms of the geometrically necessary dislocation density and the associated Burgers vector and line direction. The results are discussed in terms of potential defect formation mechanisms.

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Relating a crystal's microscopic structure-such as orientation and size-to a material's macroscopic properties is of great importance in materials science. Although most crystal orientation microscopy is performed in the scanning electron microscope (SEM), transmission electron microscopy (TEM)-based methods have a number of benefits, including higher spatial resolution. Current TEM orientation methods have either specific hardware requirements or use software that has limited scope, utility, or availability. In this article, a technique is described for orientation mapping using Kikuchi diffraction patterns generated from a focused STEM probe. One key advantage is that indexing and analysis of the patterns and maps occurs in the robust OIM Analysis software, currently widely used for electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD) analysis. It was found that with minimal to no image processing and by changing only a few software parameters, reliable indexing of Kikuchi patterns is possible. Three samples, a deformed β-Titanium (Ti), a medium carbon heat-treated steel, and BaCe0.8Y0.2O3-δ were tested to determine the effectiveness of the approach. In all three measurements the algorithms effectively and reliably determined the phases and the crystal orientations of the features measured. For the two orientation maps produced, less than 5% of the patterns were misindexed including boundary areas where overlapping patterns existed. An angular resolution of 0.15° was achieved while features <25 nm were able to be spatially resolved.

We propose a new methodology for ranking the reflectors used in traditional Hough-based indexing of electron backscatter diffraction (EBSD) patterns. Instead of kinematic X-ray or electron structure factors (Fhkl) currently utilized, we propose the integrated Kikuchi band intensity parameter (βhkl) based on integrated dynamical electron backscatter intensities. The proposed parameter is compared with the traditional kinematical intensity, , as well as the average Hough transform peak intensity, and used to index EBSD patterns for a number of different material systems of varying unit cell complexities including nickel, silicon, rutile, and forsterite. For elemental structures, βhkl closely follows the kinematical ranking. However, significant ranking differences arise for more complex unit cells, with the βhkl parameter showing a better correlation with the integrated Hough intensities. Finally, Hough-based indexing of a simulated forsterite data set showed an appreciable improvement in the median confidence index (0.15 to 0.35) when βhkl is used instead of for ranking the reflectors.

One challenge associated with indexing Electron Backscatter Diffraction (EBSD) patterns using conventional Hough-based indexing is selecting the appropriate set of reflectors. In early EBSD work, reflectors were sometimes chosen based on intensities listed in X-Ray powder diffraction tables. When the positions of the atoms in the crystal lattice are known, it is possible to calculate structure factors (Fhkl) using the kinematic simulation of diffraction. In either case, reflectors with the highest-ranking structure factors are selected as a base set. However, this base set generally requires some iterative manual tuning against experimental patterns to attain an optimal set of reflectors. This is often a difficult process even for a skilled operator, particularly for lower symmetry materials. The better the base set, the easier the refinement procedure. Generally, the kinematic structure factors provide a better starting point for the manual tuning over X-Ray intensities. A new method [1] for ranking the reflectors based on integrating dynamical simulated electron backscatter intensities within a reflection (or band) over the full diffraction sphere [2] has been proposed. The ranking metric based on this integration for a given reflector (hkl) we denote hkl. For simple structures such as face-centered-cubic structures, the dynamical hkl based ranking closely follows the kinematical Fhkl ranking. In more complex structures, the hkl ranking can depart significantly from the Fhkl ranking. In the materials investigated so far, the ranking based on the hkl parameter tends to correlate better with the bands detected by the Hough transform than the Fhkl ranking.

Many minerals in the geological realm behave as solid solutions with one of the most common of these being the Feldspar series. Combine this with lower symmetries and it can be difficult to both index and differentiate these minerals. One final complication is that the phase files available for these phases may be for chemical compositions that are much different from the actual sample. This presents many difficulties in indexing the EBSD patterns. Understanding the differences in the patterns with small changes in chemistry and atomic positions can help the analyst get more correct orientations and less noise in geological EBSD data. Using dynamically simulated EBSD patterns, it is possible to model the differences between the members of the solid solutions to come up with strategies to increase the precision and accuracy of indexing routines.

Due to continued advances in phosphor sensitivity and camera technology, electron backscattered diffraction (EBSD) within a scanning electron microscope (SEM) has become an increasingly popular method for determining crystal orientations within a given microstructure. Concurrent advances in computational processing have also made it possible to store each individual diffraction pattern as it is collected, which has allowed more complex algorithms to be deployed for post-processing and indexing patterns. This paper proposes a new post-processing technique for pattern enhancement that aids in re-indexing by leveraging a non-local smoothing kernel whose weights are based on the exponential decay of the Euclidean distance between patterns. The advantage of this approach is its ability to utilize very large smoothing kernels without losing integrity near interface boundaries and while still operating on timescales comparable to traditional indexing approaches. Using an Inconel 600 nickel alloy sample, the capabilities and performance of the proposed approach are compared to other indexing schemes, including neighbor pattern averaging with re-indexing (NPAR) and a dictionary-based approach. The results demonstrate that the proposed method consistently produces a higher index success rate (ISR) than NPAR and comparable ISRs to the dictionary-based approach, a method with orders-of-magnitude greater computational demands. Source code for the NLPAR algorithm is available at https://github.com/USNavalResearchLaboratory/NLPAR

The International Materials Research Congress (IMRC) is organized yearly at Cancun, Mexico, by the Sociedad Mexicana de Materiales (SMM) and the Materials Research Society (MRS). The conference is structured in plenary sessions, poster sessions and specialized symposia. In 2016, the XXVth IMRC conference included a topical symposium devoted to “Texture and Microstructure”. It is worth underlining that this was the very first conference ever organized in Latin America on a topic related to crystallographic texture. This symposiumranover 2 days. Thefirst day was comprised of presentations on Recrystallization, Deformation, and Substructure. The second day continued on Deformation & Substructure, Unique Applications, and Data Acquisition & Processing. Thirteen invited and seventeen regular lectures were presented as well as 3 posters. The symposium coorganizers are pleased that many of the symposium participants have accepted the invitation to submit their work for a Special Section of Advanced Engineering Materials entitled “Texture and Microstructure”. Fifteen papers were submitted for review, eleven of which were accepted for publication. In addition to contributions from the symposium, several articles were invited to complement the research presented in Cancun and we also are pleased that the authorsof six additional relevantpapers submitted directly to Advanced Engineering Materials accepted our invitation for being included in this Special Section. The study of crystallographic textures was developed to a semi-quantitative theory by the pioneering work of Guenter Wasserman and Johanna Grewen, “Texturen Metallischer Werkstoffe” (Springer-Verlag, 1962), who studied mainly industrial relevant problems by means of the analysis of twodimensional pole figures. Later, the reference book of Hans Bunge, “Texture Analysis in Materials Science Mathematical Methods”, offered a rigorous and complete methodology to determine crystallographic textures by means of a statistical Orientation Distribution Function ODF, calculated by polefigure inversion methods in the frame of spherical harmonic series. Bunge also developed a systematic method to calculate

Pseudosymmetry is a phenomenon that occurs when grains with different lattice parameters produce nearly identical diffraction patterns such that conventional electron backscatter diffraction (EBSD) techniques are unable to unambiguously differentiate the lattice orientations. This commonly occurs in materials with near-unity tetragonality, such as γ-TiAl. The current study uses cross-correlation EBSD to resolve pseudosymmetry in γ-TiAl. Three dynamically simulated reference patterns are generated for each point in the scan, one for each of the three potential pseudosymmetric orientations, which are subsequently correlated with the original pattern using six different methods in order to identify the correct orientation. The methods are first applied to a scan of dynamically simulated patterns, which is used to evaluate the sensitivity of the method to pattern resolution, pattern noise and pattern center error. It was determined that all six methods were 100% successful up to about 13 µm of pattern center error and pattern resolutions of about 80 × 80 pixels, and hence the methods were applied to an experimental sample of lamellar γ-TiAl. A hybrid combination of two of the methods was shown to successfully select the correct pseudosymmetry for about 96% of the points in the scan, improving upon the 70% accuracy of the Hough-based methods for the current study and 90% accuracy for previous studies resolving pseudosymmetry in lamellar γ-TiAl.

Twin boundaries in a crystalline material can be defined by a particular rotation angle about a particular access or a mirrored crystal orientation about a particular plane [1]. For example, copper twins are typically defined by a 60 rotation about where the associated twin plane is of the {111} family. One critical area of twin research looks at deformation twinning as the limiting factor for formability of Mg alloys, such as AZ31 [2]. In AZ31 there are two basic twin modes: compression twinning and tension twinning. The latter phenomenon forms fairly large, easy to detect twinned regions within parent grains, whereas the former tends to form extremely thin twins that are on the order of 100 nm wide. Additionally, the copper which is frequently seen in many microelectronics contains twins on the order of 10 nm [3]. In both cases these features are within the detectable limits for a modern scanning electron microscope (SEM). However, identifying these twins via crystal orientation relations with electron backscatter diffraction (EBSD) in the SEM relies on a larger spatial resolution which makes detecting these twins from crystallographic information difficult in the SEM. This study presents a method whereby improved spatial resolution of thin twins can be achieved with EBSD.

The efficacy of the dictionary approach to Electron Back-Scatter Diffraction (EBSD) indexing was evaluated through the analysis of the error in the retrieved crystal orientations. EBSPs simulated by the Callahan-De Graef forward model were used for this purpose. Patterns were noised, distorted, and binned prior to dictionary indexing. Patterns with a high level of noise, with optical distortions, and with a 25 × 25 pixel size, when the error in projection center was 0.7% of the pattern width and the error in specimen tilt was 0.8°, were indexed with a 0.8° mean error in orientation. The same patterns, but 60 × 60 pixel in size, were indexed by the standard 2D Hough transform based approach with almost the same orientation accuracy. Optimal detection parameters in the Hough space were obtained by minimizing the orientation error. It was shown that if the error in detector geometry can be reduced to 0.1% in projection center and 0.1° in specimen tilt, the dictionary approach can retrieve a crystal orientation with a 0.2° accuracy.