Electron Backscattering Pattern Research Articles

A crystal plasticity phase-field model for microstructure sensitive fatigue crack growth in a superalloy

In this work, a dislocation density-based crystal plasticity phase-field model (CP-PFM) is developed to simulate fatigue crack growth in nickel-based superalloys. Through normalization validation, the plastic dissipation work and crystallographic work are shown to be consistent with the fatigue indicator factors (FIPs), cumulative equivalent plastic strain and cumulative shear strain, and the two energies are computed as the main driving forces of the phase field. Both driving force models are able to obtain fatigue crack growth in close approximation to the experimental rate. However, the model with crystallographic work as the main driving force obtains crack growth paths that are in better agreement with electron backscattering pattern (EBSD) observations, which is attributed to its greater ability to characterize the microstructural susceptibility of fatigue crack growth. Specifically, the model is able to capture the tendency of cracks to crack along the close-packed planes and the hindering effect of grains with large misorientation angles on fatigue crack growth, which together contribute to the curved morphology of fatigue cracks. The combination of large grains or grains with small misorientation angles favors persistent slip band (PSB) formation and leads to softening of the crack tip, which results in lower fatigue crack growth rates.

Effects of service stress on the deformation behavior and microstructures of Zn-0.5Mg-0.05Fe alloy from ambient to high temperatures

To overcome challenges in the traditional melt casting process of zine alloys, such as oxidative burnout, compositional segregation, and grain coarsening, this study carried out hot compression deformation tests on Zn-0.5Mg-0.05Fe alloys prepared by powder metallurgy. The results show that increasing deformation temperature and decreasing strain rate reduce rheological stress. The hot compression deformation process exhibits three phases, as rheological stress increases, work hardening, dynamic softening, and steady-state fluidization are observed, respectively. An intrinsic equation for the hot compression process is derived as = 1.334 × 1010 × [sinh(0.0053σ)]7.62947exp(-109.931691/RT). Processing conditions for Zn-0.5Mg-0.05Fe alloy are determined from a processing map, suggesting that a safe zone of 25°C–130 °C deformation temperatures with 0.13s−1-0.36s−1 strain rates, and 120°C–200 °C deformation temperatures with 0.01s−1-0.6s−1 strain rates. Electron Back-scattering Patterns (EBSD) and Transmission Electron Microscope (TEM) results show both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) during the hot deformation compression process. DRX reduces deformation resistance, refines the grains, and improves the mechanical properties of the alloys. This study provides theoretical insights and process guidance for preparing degradable zinc alloys with excellent mechanical properties.

Machine learning based de-noising of electron back scatter patterns of various crystallographic metallic materials fabricated using laser directed energy deposition

A novel machine learning (ML) method of refining noisy Electron Back Scatter Patterns (EBSP) is proposed. For this, conditional generative adversarial networks (c-GAN) have been employed. The problem of de-noising the EBSPs was formulated as an image translation task conditioned on the input images to get refined/denoised output of EBSPs which can be indexed using conventional Hough transform based indexing algorithms. The ML model was trained using 10,000 EBSPs acquired under different settings for additively manufactured FCC, BCC and HCP alloy samples ensuring enough diversity and complexity in training data set. Pairs of noisy and corresponding optimal EBSPs were acquired by suitable tweaking of the EBSP acquisition parameters such as beam defocus, pattern binning and EBSD camera exposure duration. The trained model has brought out significant improvement in EBSD indexing success rate on test data, accompanied by betterment of indexing accuracy, quantified through ‘pattern fit’. Complete automation of the EBSP refinement was demonstrated where in entire EBSD scan data can be fed to the model to get the refined EBSPs from which high quality EBSD data can be obtained.

Effect of lamellar LPSO phase on mechanical properties and damping capacity in cast magnesium alloys

The effect of the lamellar long period stacking order (LPSO) phase on both mechanical properties and damping capacity of magnesium alloys is still vague. After heat treatment at 540 °C for 4 h and 450 °C for 10 h, the Mg-10Gd-2Y–1Zn-0.5Zr-0.2Nd (wt%) alloy with the lamellar LPSO phase is prepared to study the influence of lamellar LPSO phase on damping capacity and mechanical properties. Combined transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron back-scattering patterns (EBSD) system, it is surprisingly found that the growth direction of the lamellar LPSO phase on basal plane is nearly parallel to the slip direction of basal dislocations, which is benefit from dislocations movement on basal plane. The dislocations move on basal plane easily, lead to a relative high damping capacity. The alloy with LPSO phases shows higher ultimate tensile strength (UTS) and elongation (EL), increased from 234 MPa to 2.6% to 254 MPa and 4.6%, respectively. The lamellar LPSO phase has an attribution to UTS and EL due to its kink deformation mechanism. Therefore, the lamellar LPSO phase can be used as a functional phase to enhance the damping capacity and mechanical properties at the same time, and providing new ideas about preparing high-strength and high-damping magnesium alloy.

Revealing geometrically necessary dislocation density from electron backscatter patterns via multi-modal deep learning

The characterization of geometrically necessary dislocation (GND) is central to understanding the plastic deformation in materials. Currently, fast and accurate determination of GND density via Electron Backscatter Diffraction (EBSD) remains a challenge. Here, a multi-modal deep learning approach is proposed to predict GND density in terms of electron backscatter patterns (EBSPs) and dislocation configurations. The proposed multi-modal architecture consists of two separated convolutional neural network (CNN) processing streams. One CNN stream aims at extracting pattern shifts from EBSPs, and the other CNN stream focuses on learning suitable representations of dislocation configurations. We also introduce a specific data augmentation strategy termed neighboring pairs generating strategy for the GND prediction task. Taking the GND density from dictionary indexing-based analysis as the target property, high accuracy is achieved on several aluminum samples. Also, our networks are robust to various forms of noise, and the prediction speed is as fast as modern EBSD scanning rates, enabling real-time GND density analysis possible.

Formation of cube recrystallized grains in high-purity Al

Abstract In high-purity 4 N (99.99 wt.%) Al containing 50 wt.ppm Cu, very strong {100}<001> recrystallization textures are developed after 98% cold rolling and annealing at 500 °C. They are about three times stronger than those observed in standard high-purity 4 N Al without Cu addition. In this paper, the mechanism of the formation of such strong {100}<001> recrystallization textures were investigated in detail by using the EBSP (electron backscatter pattern) analysis. It was found that, at the earliest stage of recrystallization, {100} <001>-recrystallized grains were nucleated by forming a row lying parallel to the rolling direction and growing preferentially within the elongated deformed grain in which they were nucleated. Most of these {100}<001>-recrystallized grains had orientations very near to the exact cube orientations. {100}<001>-recrystallized grains in this materials were characterized by their rapid growth, which was observed at the later stages of recrystallization. Since they were surrounded by deformed regions having very strong β-fiber rolling textures formed by heavy cold rolling, their grain boundaries were high-angle grain boundaries with high mobility. Assisted further by high stored energy introduced by heavy rolling reductions, {100}<001>-recrystallized grains could grow very rapidly, traversing readily several deformed grains. In this material, {100}<001>-recrystallized grains were not nucleated so abundantly. However, {100}<001>-recrystallized grains were nucleated much earlier and grew much faster than recrystallized grains with other orientations. They were, therefore, always larger than recrystallized grains with other orientations. Due to such size advantages, {100}<001>-recrystallized grains could rapidly consume fine-recrystallized grains with other orientations during the subsequent grain growth process. As a result, microstructures observed after annealing at 500 °C for 2 h consisted mostly of coarse {100}<001>-recrystallized grains slightly misoriented with each other. It is, thus, rapid growth of few {100}<001>-recrystallized grains during recrystallization, and their preferential grain growth, that enhance the development of very strong {100}<001> recrystallization textures in this high-purity Al. Cu seems to suppress nucleation of recrystallized grains with other orientations.

Polarity Determination in EBSD Patterns Using the Hough Transformation

Abstract Currently, the automated electron backscatter diffraction (EBSD) technique only allows the differentiation of the Laue groups based on an electron backscatter pattern (EBSP). This article shows that information concerning the lattice plane polarity is not only stored in the EBSP, but also in the Hough transformed EBSP where it can be easily accessed for automated evaluation. Polar Kikuchi bands lead to asymmetric peaks during the Hough transformation that are dependent on the atomic number difference of the involved atoms. The effect can be strong enough to be detected when evaluating the intensities of the regular excess and deficiency lines. Polarity detection from the Hough transformation of an EBSP cannot only enhance the utility of the EBSD technique and expand the information gained from it, but also illustrates a path toward automated polarity determination during EBSD scans.

Indexation of electron diffraction patterns at grain boundaries

Grain boundaries play a vital role in materials science, and they are extensively studied through experimental and numerical methods. Electron backscatter diffraction (EBSD) is commonly used to characterize crystalline materials, yet its performance is often compromised at grain boundaries. The key difficulty is to index the overlapped electron backscatter patterns, where Kikuchi bands from multiple crystal orientations coexist. Hough-indexation often fails in treating overlapped EBSP, while the recently proposed dictionary indexation and sphere indexation give only one triplet of Euler angles from overlapped patterns. For all these methods, the orientation indexing precision drops for overlapped EBSP. Here we propose an integrated Digital Image Correlation (DIC) procedure to determine simultaneously and precisely multiple crystal orientations by registering the overlapped EBSP and the master pattern. The contribution ratio of each crystal orientation to the overlapped pattern is also available. Through an experimental EBSD dataset around a triple point, multiple benefits of the rich results from the method are demonstrated, such as refining grain boundaries, revealing EBSD scan errors and quantifying spatial resolution of EBSD. At the grain boundaries, the crystal orientation measurement uncertainty is 0.03∘ for both indexed crystal orientations, the same order for grain interiors, while their contribution ratios of uncertainty around 0.02 are obtained.

The EBSD spatial resolution of a Timepix-based detector in a tilt-free geometry

Performing EBSD with a horizontal sample and a parallel EBSD detector sensor, enables safer specimen movements for data collection of large specimen areas and improves the longitudinal spatial resolution. The collection of electron backscattering patterns (EBSPs) at normal incidence to the electron beam has been revisited via the use of a direct electron detection (DED) sensor. In this article we present a fully operational DED EBSD detection system in this geometry, referred to as the tilt-free geometry. A well-defined Σ=3[101]{121} twin boundary in a Molybdenum bicrystal was used to measure the physical spatial resolution of the EBSD detector in this tilt-free geometry. In this study, two separate methods for estimating the spatial resolution of EBSD, one based on a pattern quality metric and the other on a normalised cross correlation coefficient were used. The spatial resolution was determined at accelerating voltages of 8 kV, 10 kV, 12 kV, 15 kV and 20 kV ranging from ~22−38 nm using the pattern quality method and ~31−46 nm using the normalised cross correlation method.

Evaluation of Phonon Dispersion Relation for Bulk Silicon Germanium by Inelastic X-ray Scattering

1. Introduction Silicon germanium (SiGe) is one of the promising candidates as a next-generation material for thermoelectric devices as an ambient energy harvesting technique because it has low thermal conductivity. For a SiGe thermoelectric device, it is important to reveal the phonon scattering mechanism for the alloy material and the thermal transport in miniaturization to the nanoscale. However, the origin of the low thermal conductivity of the SiGe alloy has not been investigated in a sufficiently rigorous manner yet. In addition, the correlation among the thermal conductivity, the phonon dispersion curve, and the lifetime remains mostly unclear.From the above, we focused on direct phonon properties evaluation by inelastic X-ray scattering (IXS) with synchrotron radiation. IXS is a powerful technique that reveals the phonon dispersion curves in contrast to Raman spectroscopy, which can only give optical phonon modes at the Brillouin zone center (the Γ point). In this study, we evaluated the phonon dispersion curve of bulk SiGe by IXS. 2. Experimental method The single-crystalline SiGe samples for IXS were prepared by two different growth methods: the Czochralski (Cz) [1] and traveling liquidus zone (TLZ) methods [2]. The sample information is summarized in Table 1. Prior to the IXS measurements, the crystal orientation and Ge fraction were confirmed by X-ray diffraction (XRD) and electron backscattering pattern (EBSP) measurements, respectively.The IXS measurements were performed at the BL35XU beamline of the SPring-8 synchrotron facility. The measurements were conducted at room temperature using a reflection geometry. The incident X-ray energy was set to 17.795 keV, which corresponds to Si (9 9 9) reflection, and the overall energy resolution was around 3 meV. The incident X-ray beam size was approximately 60 x 75 μm2. The measurements were conducted along the Γ-X ([00q]) direction. 3. Results and Discussion As an example of phonon dispersion of bulk Si1-x Ge x , we show the IXS results of x = 0.45 in Fig. 1 obtained by peak positions of IXS spectra. As a result, all optical and acoustic phonon modes for bulk SiGe were observed as shown in Fig. 1. In addition, the energy of the optical phonon modes (Si-Si, Si-Ge, and Ge-Ge modes) obtained by IXS at the zone center (Γ point) was good agreement with results of Raman spectroscopy (λ = 532 nm). Both Raman and IXS indicate that, at around Γ point, the phonon energies of Si-Si and Ge-Ge modes tend to be lower than that of pure Si and Ge, respectively. These behaviors can be considered to be caused by random distribution of Si and Ge atoms in the alloy. On the other hand, it was revealed that the acoustic phonon (LA and TA modes) energies are located between those of pure Si [3] and Ge [4]. Based on the above, the origin of the dramatic thermal conductivity reduction of the SiGe alloy, which has been reported in previous study [5], may not be derived from the reduction of group velocity, but the low phonon lifetime reduction. Acknowledgements The IXS measurements were performed at SPring-8 with the approval of JASRI (Proposal Nos. 2016A1496, 2017B1630, 2019A1678, and 2019B1750). The authors thank Dr. Koji Usuda (KIOXIA Corp.) for his great support with analyzing the IXS results throughout the work.

Processing and indexing of electron backscatter patterns using open-source software

A new method to increase the signal-to-noise ratio S/N of electron backscatter patterns (EBSPs) based upon principal component analysis (PCA) is presented. The PCA denoising method is applied to ten scans of EBSPs from the same region of interest of a recrystallised nickel sample acquired with a decreasing S/N, achieved by reducing the exposure time while increasing the camera gain accordingly. That PCA denoising increases S/N in EBSPs is demonstrated by comparing indexing success rates after both Hough and dictionary indexing (HI and DI) of the Ni patterns having undergone one of four processing routes: i) standard static and dynamic background corrections (standard corrections), ii) standard corrections and pattern averaging with the four closest neighbours, iii) standard corrections and PCA denoising, and iv) standard corrections and pattern averaging followed by PCA denoising. Both pattern averaging and PCA denoising increases the indexing success rates for both indexing approaches for the studied Ni scans, with the former processing route providing the better success rates. The best success rates are obtained after pattern averaging followed by PCA denoising. The potential of PCA denoising to reveal additional pattern details compared to standard corrections and pattern averaging is demonstrated in a pattern from an orthoclase (KAlSi3O8) grain in a geological sample. Software code, and the Ni data sets, are released alongside this article as part of KikuchiPy, an open-source software package dedicated to processing and analysis of EBSPs.

Discriminating β, α and α″ phases in metastable β titanium alloys via segmentation: A combined electron backscattering diffraction and energy-dispersive X-ray spectroscopy approach

Annealed metastable β titanium (Ti) alloys comprise body-centred-cubic β and hexagonal-close-packed α phases and possibly, orthorhombic α″ martensite that forms on quenching or deformation. Electron backscattering diffraction is amongst the most popular methods for characterising such multi-phase microstructures. However, the crystallographic similarity between α and α″ martensite renders unambiguous discrimination of these phases via electron backscattering patterns (EBSPs) virtually impossible; thereby limiting the use of EBSD in characterising β-Ti alloys. In this study, we demonstrate that α and α″ martensite are primarily misindexed due to an indiscernible difference between these phases along their [1¯10]α and [010]α″ zone axes. Furthermore, the slight compositional difference between α and α″ is insufficient to discriminate these phases using on-the-fly energy-dispersive X-ray spectroscopy (EDS) spectrum matching. Consequently, a segmentation method was developed that relies on a combination of reindexed EBSPs and grain-median EDS elemental data to unambiguously discriminate β, α and α″ martensite in metastable β Ti alloys. All steps are implemented in an open-source and freely available computer program called phaseSegmenter that makes use of the MTEX toolbox in MATLAB. The program is readily applicable to Ti alloys containing α′, α″ or massively transformed α as well as other phase transforming alloy systems with similar phase discrimination issues.

Dictionary Indexing of Electron Back-Scatter Diffraction Patterns: a Hands-On Tutorial

Dictionary indexing of electron back-scatter patterns was recently proposed as an alternative to the commercially available indexing packages. In this tutorial paper, we describe in detail the various steps that need to be taken to successfully complete an indexing run on an arbitrary data set. We provide three toy data sets for the reader to experiment with: poly-crystalline nickel with several different acquisition conditions, orthorhombic forsterite, and a single slice from a large serial sectioning experiment on a Ni-based superalloy. The data files and all files produced by the indexing routine are made available as Supplementary Material (https://doi.org/10.1184/R1/7792505).

Pattern matching analysis of electron backscatter diffraction patterns for pattern centre, crystal orientation and absolute elastic strain determination – accuracy and precision assessment

Pattern matching between target electron backscatter patterns (EBSPs) and dynamically simulated EBSPs was used to determine the pattern centre (PC) and crystal orientation, using a global optimisation algorithm. Systematic analysis of error and precision with this approach was carried out using dynamically simulated target EBSPs with known PC positions and orientations. Results showed that the error in determining the PC and orientation was <10−5 of pattern width and <0.01° respectively for the undistorted full resolution images (956 × 956 pixels). The introduction of noise, optical distortion and image binning was shown to have some influence on the error although better angular resolution was achieved with the pattern matching than using conventional Hough transform-based analysis. The accuracy of PC determination for the experimental case was explored using the High Resolution (HR-) EBSD method but using dynamically simulated EBSP as the reference pattern. This was demonstrated through a sample rotation experiment and strain analysis around an indent in interstitial free steel.

AstroEBSD: exploring new space in pattern indexing with methods launched from an astronomical approach

Electron backscatter diffraction (EBSD) is a technique used to measure crystallographic features in the scanning electron microscope. The technique is highly automated and readily accessible in many laboratories. EBSD pattern indexing is conventionally performed with raw electron backscatter patterns. These patterns are software processed to locate the band centres (and sometimes edges) from which the crystallographic index of each band is determined. Once a consistent index for many bands is obtained, the crystal orientation with respect to a reference sample and detector orientation can be determined and presented. Unfortunately, because of challenges related to crystal symmetry, there are limited available pattern-indexing approaches and this has probably hampered open development of the technique. In this article, a new method of pattern indexing is presented, based upon a method with which satellites locate themselves in the night sky, and its effectiveness is systematically demonstrated using dynamical simulations and real experimental patterns. The benefit of releasing this new algorithm as open-source software is demonstrated when this indexing process is utilized, together with dynamical solutions, to provide some of the first accuracy assessments of an indexing solution. In disclosing a new indexing algorithm, and software processing toolkit, the authors hope to open up EBSD developments to more users. The software code and example data are released alongside this article for third party developments.

Shock metamorphic history of &gt;4 Ga Apollo 14 and 15 zircons

AbstractDuring impact events, zircons develop a wide range of shock metamorphic features that depend on the pressure and temperature conditions experienced by the zircon. These conditions vary with original distance from impact center and whether the zircon grains are incorporated into ejecta or remain within the target crust. We have employed the range of shock metamorphic features preserved in &gt;4 Ga lunar zircons separated from Apollo 14 and 15 breccias and soils in order to gain insights into the impact shock histories of these areas of the Moon. We report microstructural characteristics of 31 zircons analyzed using electron beam methods including electron backscatter pattern (EBSP) and diffraction (EBSD). The major results of this survey are as follows. (1) The abundance of curviplanar features hosting secondary impact melt inclusions suggests that most of the zircons have experienced shock pressures between 3 and 20 GPa; (2) the scarcity of recrystallization or decomposition textures and the absence of the high‐pressure polymorph, reidite, suggests that few grains have been shocked to over 40 GPa or heated above 1000 °C in ejecta settings; (3) one grain exhibits narrow, arc‐shaped bands of twinned zircon, which map out as spherical shells, and represent a novel shock microstructure. Overall, most of the Apollo 14 and 15 zircons exhibit shock features similar to those of terrestrial zircon grains originating from continental crust below large (~200 km) impact craters (e.g., Vredefort impact basin), suggesting derivation from central uplifts or uplifted rims of large basins or craters on the Moon and not high‐temperature and ‐pressure ejecta deposits.

Evaluation of Laterally Graded Silicon Germanium Wires for Thermoelectric Devices Fabricated by Rapid Melting Growth

1.Introduction SiGe is promising candidates for the excellent thermoelectric device material with low thermal conductivity by alloy effect. In order to improve thermoelectric performance, it needs to realize high Seebeck coefficient of SiGe. From the above, we focused on the laterally graded SiGe wires fabricated by rapid melting growth (RMG) [1]. It has been reported that laterally graded energy-band-gap structures in SiGe can enhance thermoelectric performance using simulation [2]. However, the laterally graded SiGe wire structures for thermoelectric devices has not been investigated. In this study, the RMG laterally graded SiGe wire structures for thermoelectric devices were evaluated to achieve high thermoelectric performance. 2.Experiment The RMG laterally graded SiGe wires were grown on a silicon-on-insulator (SOI) wafer. The SOI wafer with 45 nm thick was patterned to form the Si island seeds. Then, amorphous Si0.15Ge0.85 film was deposited by molecular beam deposition. After the patterning of wires, 1 μm thick capping SiO2 layer was deposited by plasma-enhanced chemical vapor deposition (PECVD), and the RMG were performed at 1100 ℃ in N2 ambient. The size of the SiGe wires are 10 mm in length, 3 mm in width and 100 nm in thickness, respectively. Finally, both end parts of the SiGe wires were connected to 1 μm thick Al thermal and electrical conductive pads. The RMG laterally graded SiGe wires were evaluated by Raman spectroscopy and electron back-scattering pattern (EBSP). A quasi-line excitation (approximately 100 μm) was used for Raman spectroscopy. Excitation source of visible laser (λ = 532 nm) was used and focal length of the Raman spectrometer was 2,000 mm. Wavenumber resolution is approximately 0.1 cm-1. One dimensional measurements with a quasi-line excitation source were performed at the same time to evaluate Ge concentration x in the Si1-x Ge x wires. Moreover, the change of crystal orientation in the SiGe wires was measured by EBSP. 3. Results and Discussion Figure 1 shows one-dimensional distribution of Raman spectra for Ge-Ge mode obtained by Raman spectroscopy using a quasi-line excitation. As shown in Fig. 1, an apparent change of Raman shift was observed along the wire. As an increase in distance from the Si seed, the Raman peak positions in the SiGe wires for Ge-Ge modes shifted toward higher wavenumbers. Figure 2 shows Ge concentration x distribution using the Raman shifts for Ge-Ge mode. Ge concentration x and the theoretical values were calculated by using Raman shift equation for Ge-Ge mode in Ref. 3 on the basis in strain-free assumption and Scheil equation in Ref. 4, respectively [3, 4]. As a result, we confirmed that the calculated Ge concentration x is lower than the theoretical values. It is considered that the Raman peak positions for Ge-Ge mode are shifted not only by Ge concentration x but also by a strain in the SiGe wire. Crystal orientation mapping obtained by EBSP was shown in Fig. 3. Here, the rotating angles are defined as the changes in the crystal orientations from those of the Si seed. The angles increase with distance from the Si seed. This rotation of crystal orientation may also influence electronic and thermoelectric performance as well as graded Ge concentration. We will report the thermoelectric properties of the RMG laterally graded SiGe wire for thermoelectric devices. Acknowledgements This work was supported by CREST, JST (JPMJCR15Q7), PRESTO, JST (JPMJPR15R2), and the Japan Society for the Promotion of Science through a JSPS Fellows (17J08240).

Evaluation of Laterally Graded Silicon Germanium Wires for Thermoelectric Devices Fabricated by Rapid Melting Growth

To achieve high thermoelectric performance, laterally graded silicon germanium (SiGe) wires were fabricated by rapid melting growth (RMG) method. In addition, the structure evaluation of the RMG laterally graded SiGe wire were performed by Raman spectroscopy and electron backscattering pattern (EBSP). Ge fraction x and strain were estimated from one-dimensional distribution of Raman shift for Ge-Ge mode. As a result, an apparent change of Ge fraction x was observed. For, biaxial isotropic strain assumption, good agreement among the obtained Ge fraction x distribution and theoretical values in the RMG laterally graded SiGe wire near Si seed area were shown. Crystal orientation mapping was obtained by EBSP. It was revealed that the crystal orientation in the SiGe wire was changed from [001] to [110] with increasing growth length. These changes may also influence electronic and thermoelectric performance dramatically.

A consistent full-field integrated DIC framework for HR-EBSD

A general, transparent, finite-strain Integrated Digital Image Correlation (IDIC) framework for high angular resolution EBSD (HR-EBSD) is proposed, and implemented through a rigorous derivation of the optimization scheme starting from the fundamental brightness conservation equation in combination with a clear geometric model of the Electron BackScatter Pattern (EBSP) formation. This results in a direct one-step correlation of the full field-of-view of EBSPs, which is validated here on dynamically simulated patterns. Strain and rotation component errors are, on average, (well) below 10−5 for small (Eeq=0.05%) and medium (Eeq=0.2%) strain, and below 3×10−5 for large strain (Eeq=1%), all for large rotations up to 10° and 2% image noise. High robustness against poor initial guesses (1° misorientation and zero strain) and typical convergence in 5 iterations is consistently observed for, respectively, image noise up to 20% and 5%. This high accuracy and robustness rivals, when comparing validation on dynamically simulated patterns, the most accurate HR-EBSD algorithms currently available which combine sophisticated filtering and remapping strategies with an indirect two-step correlation approach of local subset ROIs. The proposed general IDIC/HR-EBSD framework lays the foundation for future extensions towards more accurate EBSP formation models or even absolute HR-EBSD.

Quantitative electron backscatter diffraction (EBSD) data analyses using the dictionary indexing (DI) approach: Overcoming indexing difficulties on geological materials

Electron backscatter diffraction (EBSD) data yield plentiful information on microstructure and texture of natural as well as experimentally produced mineral and rock samples. For instance, the characterization of microstructures and textures by EBSD allows for the evaluation of phase equilibria. Furthermore, determination of the preferred orientations of crystals using EBSD yields constraints on deformation mechanisms and history of the minerals/rocks. The latter affects bulk-rock properites, for example, through the relation between lattice preferred orientation and electrical conductivity and seismic anisotropy. EBSD is also applied to advance our understanding of various phenomena such as seismic wave attenuation in the Earth deep interior and its relation to the presence of interfacial small degrees of melt fractions, or free fluid phases. In standard EBSD software solutions, the original EBSD patterns are rarely saved and indexing routines result in many artifacts, such as pseudo-symmetry or unindexed pixels at interfaces that may be misinterpreted as amorphous material, such as a melt. Here we report the first application of the dictionary indexing (DI) approach proposed by Chen et al. (2015), an alternative indexing routine, which we extended to be applicable to multiphase geologic materials. The DI method is independent of the EBSD system, and thus of the used detector/software. The DI routine generates simulated EBSD patterns for all possible crystal orientations, taking the sample composition and experimental setups into account. The resulting pattern database is called a dictionary. The experimental electron backscattering pattern (EBSP) images are indexed by comparing them to the dictionary using a dot-product algorithm. We evaluate the new DI method in comparison to standard routines and highlight advantages and disadvantages. To test and compare the DI’s reliability and performance, we apply the routine to two scientifically challenging samples: (1) A nominally anhydrous (“dry”) residual eclogite composed of garnet (cubic), clinopyroxene (monoclinic) and an amorphous melt, where the different degrees of hardness of the phases cause surface topology; and (2) a pure forsterite (olivine) polycrystalline sample produced by vacuum sintering. The acquired EBSD patterns are of low quality for the latter as a result of fast data acquisition to reduce the on-line machine time. We conclude that the new DI method is highly precise and surpasses the performance of previously available methods, while being computer time and computer memory consuming. We find that the DI method is free of pseudo-symmetry-related problems. Interpolation of data becomes obsolete and high reproducibility is obtained, which minimizes the operator impact on the final data set. The latter is often caused by applying several cleaning steps on EBSD maps with low indexing fraction. Finally, much higher scientific integrity is ensured by image collections as described above, which requires that all patterns are saved. This in turn allows later re-analyses if required. The DI routine will help to achieve more reliable information on interface properties of geological samples, including amorphous materials, and thus in the long run help to improve the accuracy of large-scale Earth mantle process models.