The electron back-scattered diffraction (EBSD) technique has been applied to fine-grained kaolin minerals to determine the polytypes (kaolinite, dickite and nacrite) of individual grains and their crystallographic orientations in a scanning electron microscope (SEM). Because kaolin minerals are prone to radiation damage by the intense electron beam necessary to obtain EBSD patterns, the beam has to be rastered across the specimens during pattern acquisition. Kaolinite-dickite and nacrite are easily distinguished by their trigonal or hexagonal symmetry about the [001]* direction, respectively, of the Kikuchi bands with k = 3n. Dickite can be differentiated from kaolinite by mirror symmetry parallel to the a-c plane, and by the characteristic contrast of HOLZ rings.

As EBSD analysis is performed using a SEM, morphological characters can be correlated with polytypes. Dickite fragments could be discerned as oriented overgrowths on nacrite plates. Dickite was observed to always adopt euhedral shapes in a diagenetic mixture of kaolinite and dickite. Lath-shaped dickite is elongated along the a axis direction. Rhombohedral dickite consists of crystals with {1̄11} indexed to the side facets.

Polytypism in gümbelite and its relationship to the fibrous or ribbon-like morphology exhibited by this Mg-rich illite were investigated by powder X-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). Comparison between the XRD pattern from oriented fibers using a conventional powder diffractometer and a randomly oriented pattern using a Gandolfi camera suggested that 2M2 is dominant but other polytypes belonging to subfamily A also exist, and that the fiber axis of gümbelite is parallel to <110> in 2M2, <110> in 2M1, and <100> in 1M. The EBSD analyses confirmed these crystallographic directions directly from individual crystals. Electron diffraction and high-resolution TEM showed that twinning and intergrowths of various polytypes including both subfamilies are common in a single crystal and that the two types of rotations [2n60° and (2n+1)60°] between adjacent layers are often randomly mixed at the monolayer level. The data suggest that high densities of twinning and intergrowths account for the origin of the fibrous morphology along <110> for 2M1 and 2M2 polytypes. Volume restriction in a confined vein space may also play a role.

Zaykovite, ideally Rh3Se4, is a new mineral, the first natural rhodium selenide. It was discovered in the assemblages of platinum-group minerals from the Kazan gold placer, South Urals, Russia. The mineral occurs as crystals up to 40 μm in size within the grains of Pt3Fe alloy, in association with unnamed Pd–Sb–Te phase and Au–Pd alloy. In reflected light, zaykovite has a grey colour with bluish-greenish tint; it shows weak bireflectance and anisotropy. Reflectance values [Rmax/Rmin (%) for COM approved wavelengths (nm)] are: 30.1/29.3(470), 32.2/31.0(546), 33.4/32.0(589) and 35.1/33.7(650). The chemical composition corresponds to the empirical formula (Rh2.26Pt0.46Ir0.25Ru0.01Pd0.01Fe0.01)Σ3.00(Se2.77S1.21Te0.02)Σ4.00 Zaykovite is monoclinic, space group C2/m, a = 10.877(1), b = 11.192(1), c = 6.4796(6) Å, β = 108.887(2)°, V = 746.3(1) Å3, Z = 6 and Dcalc = 8.32 g cm–1. The crystal structure has been solved and refined to R1 = 0.016 based on 858 unique observed reflections. The strongest lines of the powder X-ray diffraction pattern [d(Å), (I), (hkl)] are: 5.43(37)($\bar{1}$11), 3.275(75)(310), 3.199(100)($\bar{1}$31), 3.061(87)(002), 2.568(62)(400), 2.545(41)(041), 3.413(34)($\bar{2}$41) and 1.697(34)(441). Zaykovite is a Se analogue of kingstonite, Rh3S4. A continuous series of solid solutions between kingstonite and zaykovite was encountered in the samples from the Kazan placer. The possible sources of this unique Rh–Se mineralisation in the South Urals could be serpentinised dunite–harzburgite or gabbro–clinopyroxenite–dunite complexes in the vicinity.

Calcite veins are common in organic-rich mudrocks, but their genesis and ability to transmit fluids are debated. A combined microstructural and isotopic investigation of an array of calcite veins recovered in core from the Marcellus Formation reveals that the veins grew via a combination of continuous fibrous growth and punctuated fracture-opening increments. Continuous opening is the result of pressure-solution creep and involves no mechanical fracturing, but rather the growth of a pressure fringe around a pre-existing, sealed fracture. In contrast, incremental opening is accomplished by overpressured, mineral-saturated fluid, which repeatedly ruptures the rock at the cement / host-rock interface. Punctuated growth increments occurred repeatedly throughout an otherwise protracted, continuous growth history, indicating that the present structures preserve hybrid deformation conditions between brittle, fluid-assisted cracking and plastic strain. Stable isotopic signatures match those of a regional opening-mode fracture set that formed in response to catagenetic fluid overpressures amid a tectonically imposed (Alleghanian) stress field. It is concluded that calcite veins form as opening-mode hydraulic fractures and are susceptible to increments of brittle reactivation, even while inelastic growth processes widen and fill the veins with fibrous cement.

Scroll-like crystals of molybdenite, 2–5 mm in size, were found in phengite rock from the outer contact of the granular quartz vein of the Kyshtym quartz deposit. Platy and partly scrolled molybdenite occur in the same phengite rock from the outer contact of the quartz–feldspar pegmatite of the Slyudyanogorsk mica deposit. Both occurrences are located in the Ufaley metamorphic block in the South Urals. Scroll-like molybdenite crystals can associate with platy and partly twisted crystals in the same samples. The chemical composition of molybdenite was studied by inductively coupled plasma mass spectrometry (ICP-MS) and electron probe microanalysis (EPMA). Polytypes of molybdenite were identified with electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD). Both scroll-like and platy molybdenite crystals are only represented by the 3R polytype, are enriched in Re up to 1 wt.% and contain no other significant impurities. Scroll-like molybdenite is twisted mainly around the crystallographic axis X. Twinning with a rotation of 60 degrees around the Z crystallographic axis is fixed in the plane (ab). The most probable origin of scroll molybdenites is the consequent growth of molybdenite around nucleation centres, which are commonly represented by mica crystals. The formation of the 3R polytype is caused by the difference in dimension of the layers enriched and depleted in rhenium.

In this study, binary as-cast Al–Cu alloys: Al25Cu (Al–25%Cu) and Al45Cu (Al–45%Cu) (in wt%) were severely plastically deformed by extrusion combined with a reversible torsion (KoBo) method to produce an ultrafine-grained structure (UFG). The binary Al–Cu alloys consist of α-Al and intermetallic Al2Cu phases. The morphology and volume fraction of α-Al and Al2Cu phases depend on the Cu content. The KoBo process was carried out using extrusion ratios of λ = 30 and λ = 98. The effect of phase refinement has been studied by means of scanning electron microscopy with electron backscattering diffraction and scanning transmission electron microscopy. The mechanical properties were assessed using compression tests. Detailed microstructural analysis shows that after the KoBo process, a large number fraction of high-angle boundaries (HABs) and a very fine grain structure (~2–4 μm) in both phases are created. An increase of λ ratio during the KoBo processing leads to a decrease in average grain size of α-Al and Al2Cu phases and an increase in fraction of HABs. UFG microstructure and high fraction of HABs provide the grain boundary sliding mechanism during KoBo deformation. UFG microstructure contributes to the enhanced mechanical properties. Compressive strength (Rc) of Al25Cu alloy increases from 172 to 340 MPa with an increase of λ. Compressive strain (Sc) for Al25Cu alloy increased from 35 to 67% with an increase of λ. High fraction of intermetallic phase in Al45Cu alloy was responsible for room temperature strengthening of alloy and low compressive strain. The deformed Al45Cu alloy with λ = 30 showed that Rc is 194 MPa and Sc is equal to 10%.

A common problem in analytical scanning electron microscopy (SEM) using electron backscatter diffraction (EBSD) is the differentiation of phases with distinct chemistry but the same or very similar crystal structure. X-ray energy dispersive spectroscopy (EDS) is useful to help differentiate these phases of similar crystal structures but different elemental makeups. However, open, automated, and unbiased methods of differentiating phases of similar EBSD responses based on their EDS response are lacking. This paper describes a simple data analytics-based method, using a combination of singular value decomposition and cluster analysis, to merge simultaneously acquired EDS + EBSD information and automatically determine phases from both their crystal and elemental data. I use hexagonal TiB2 ceramic contaminated with multiple crystallographically ambiguous but chemically distinct cubic phases to illustrate the method. Code, in the form of a Python 3 Jupyter Notebook, and the necessary data to replicate the analysis are provided as Supplementary material.

As the feature size of crystalline materials gets smaller, the ability to correctly interpret geometrical sample information from electron backscatter diffraction (EBSD) data becomes more important. This paper uses the notion of transition curves, associated with line scans across grain boundaries (GBs), to correctly account for the finite size of the excitation volume (EV) in the determination of the geometry of the boundary. Various metrics arising from the EBSD data are compared to determine the best experimental proxy for actual numbers of backscattered electrons that are tracked in a Monte Carlo simulation. Consideration of the resultant curves provides an accurate method of determining GB position (at the sample surface) and indicates a significant potential for error in determining GB position using standard EBSD software. Subsequently, simple criteria for comparing experimental and simulated transition curves are derived. Finally, it is shown that the EV is too shallow for the curves to reveal subsurface geometry of the GB (i.e., GB inclination angle) for most values of GB inclination.

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.

This work presents the microstructure of the cross-section of a newly developed Nb/Inconel 601 weld with particular attention paid to the continuity, morphology of the interface, and the microstructural changes within its vicinity. Both scanning (SEM) and transmission (TEM) electron microscopy techniques are excellent tools to analyze the microstructure that affects both mechanical and corrosion resistance properties of the obtained product. Grain size examination and their orientation together with the character of grain boundaries by the electron backscattered diffraction (EBSD) technique were performed followed by chemical composition determination across the interface with energy-dispersive X-ray spectroscopy (EDS) in SEM. Then, the microstructure observations of the mixed region located at the Nb/Inconel 601 interface using the TEM technique allowed its chemical and phase composition to be revealed.

Methods within the domain of artificial intelligence are gaining traction for solving a range of materials science objectives, notably the use of deep neural networks for computer vision for the analysis of electron diffraction patterns. An important component of deploying these models is an understanding of the performance as experimental diffraction conditions are varied. This knowledge can inspire confidence in the classifications over a range of operating conditions and identify where performance is degraded. Elucidating the relative impact of each parameter will suggest the most important parameters to vary during the collection of future training data. Knowing which data collection efforts to prioritize is of concern given the time required to collect or simulate vast libraries of diffraction patterns for a wide variety of materials without considering varying any parameters. In this work, five parameters, frame averaging, detector tilt, sample-to-detector distance, accelerating voltage, and pattern resolution, essential to electron diffraction are individually varied during the collection of electron backscatter diffraction patterns to explore the effect on the classifications produced by a deep neural network trained from diffraction patterns captured using a fixed set of parameters. The model is shown to be resilient to nearly all the individual changes examined here.

Myrmekites occurring in monzodiorite from the Meichuan pluton in the Dabie ultrahigh-pressure metamorphic belt were investigated. The petrographic evidence demonstrates a metasomatic origin for myrmekite formation at the scale of individual alkali feldspar grains, and that the myrmekitic quartz and plagioclase matrix are generated simultaneously replacing precursor feldspar. Energy-dispersive X-ray spectroscopy and electron microprobe analysis indicate a low anorthite content in the narrow rim of host plagioclase near the myrmekite–alkali-feldspar interface. The Ca2+, Na+ proportion of hydrothermal fluids replacing precursor alkali feldspar is 1:5.4, calculated from the anorthite content of the inner part of the host plagioclase and the neighbouring alkali feldspar. Electron back-scattered diffraction was used to identify the crystallographic orientation of the myrmekitic quartz, plagioclase matrix and the precursor alkali feldspar. The crystallographic orientation relationships (110)Kfs//(11$\bar{2}\bar{1}$)Qtz, (20$\bar{1}$)Kfs//(11$\bar{2}$1)Qtz and [11$\bar{2}3]$Qtz//[001]Kfs between myrmekitic quartz and adjacent alkali feldspar were obtained from statistical analysis. No clear crystallographic orientation relationship between quartz and plagioclase was found. The growth of myrmekitic quartz is constrained by the precursor alkali feldspar rather than the simultaneously crystallised plagioclase. This research is helpful for understanding the intergrowth mechanism during metasomatism.

Electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) are used to extract crystallographic information from bulk samples, such as their crystal structure and orientation as well as the presence of any dislocation and grain boundary defects. These techniques rely on the backscattered electron signal, which has a large distribution in electron energy. Here, the influence of plasmon excitations on EBSD patterns and ECCI dislocation images is uncovered by multislice simulations including inelastic scattering. It is shown that the Kikuchi band contrast in an EBSD pattern for silicon is maximum at small energy loss (i.e., few plasmon scattering events following backscattering), consistent with previous energy-filtered EBSD measurements. On the other hand, plasmon excitation has very little effect on the ECCI image of a dislocation. These results are explained by examining the role of the characteristic plasmon scattering angle on the intrinsic contrast mechanisms in EBSD and ECCI.

An Al–Cu–Li aerospace alloy has been investigated to determine the order in which corrosion at different types of sites occurs in AA2099-T83. Specifically, the sequence of galvanic attack on intermetallic (IM) particles and other sites of AA2099-T83 was determined as a function of time, in 0.1 M NaCl, through the use of scanning electron microscopy and electron backscatter diffraction characterization techniques. The earliest attack occurred at isolated grains and grain boundaries and on Li-containing dispersoids. Similarly, some constituent IM particles showed evidence of trenching in the surrounding alloy matrix. These IM particles included Al7Cu2Fe and another group of unidentified particles which displayed complete trenching within the first 10 min of exposure. Al13(Fe, Mn)4 were next most active followed by Al37Fe12Cu2 with Al6(Fe,Mn) and large TiB2 particles being the least active.

Samples from the sphalerite-dominated zone of a seafloor massive sulfide chimney, the Satanic Mills Chimney of the PACMANUS hydrothermal field, have been investigated to determine the internal macrostructure and microstructure of this zone, the phases present, and the distribution of metals. A combination of electron probe microanalysis, electron backscattered diffraction, and x-ray diffraction has been used. At the macroscale, this zone of the chimney wall is heavily porous and is comprised primarily of sphalerite, enclosing minor chalcopyrite, pyrite, and wurtzite. A Pb–As sulfosalt layer of possible microbial origins is present at the outer edge of the sphalerite matrix, next to a pore. The sphalerite has grown in globules on the order of 300 μm in diameter. At the microscale, the sphalerite features a colloform texture and a duplex-type grain structure consisting of either fine-grain regions in the center surrounded by coarse-grained regions or radiating coarse grains only. Pb- and As-rich bands have been detected in the colloform sphalerite, and growth twins have been observed in both the sphalerite and chalcopyrite crystals. A qualitative description of the growth of a typical globule is given, including nucleation, crystal growth, and solute redistribution.

Electron backscatter diffraction (EBSD) is one of the primary tools in materials development and analysis. The technique can perform simultaneous analyses at multiple length scales, providing local sub-micron information mapped globally to centimeter scale. Recently, a series of technological revolutions simultaneously increased diffraction pattern quality and collection rate. After collection, current EBSD pattern indexing techniques (whether Hough-based or dictionary pattern matching based) are capable of reliably differentiating between a “user selected” set of phases, if those phases contain sufficiently different crystal structures. EBSD is currently less well suited for the problem of phase identification where the phases in the sample are unknown. A pattern analysis technique capable of phase identification, utilizing the information-rich diffraction patterns potentially coupled with other data, such as EDS-derived chemistry, would enable EBSD to become a high-throughput technique replacing many slower (X-ray diffraction) or more expensive (neutron diffraction) methods. We utilize a machine learning technique to develop a general methodology for the space group classification of diffraction patterns; this is demonstrated within the $\lpar 4/m\comma \;\bar{3}\comma \;\;2/m\rpar$ point group. We evaluate the machine learning algorithm's performance in real-world situations using materials outside the training set, simultaneously elucidating the role of atomic scattering factors, orientation, and pattern quality on classification accuracy.

The emergence of commercial electron backscatter diffraction (EBSD) equipment ushered in an era of information rich maps produced by determining the orientation of user-selected crystal structures. Since then, a technological revolution has occurred in the quality, rate detection, and analysis of these diffractions patterns. The next revolution in EBSD is the ability to directly utilize the information rich diffraction patterns in a high-throughput manner. Aided by machine learning techniques, this new methodology is, as demonstrated herein, capable of accurately separating phases in a material by crystal symmetry, chemistry, and even lattice parameters with fewer human decisions. This work is the first demonstration of such capabilities and addresses many of the major challenges faced in modern EBSD. Diffraction patterns are collected from a variety of samples, and a convolutional neural network, a type of machine learning algorithm, is trained to autonomously recognize the subtle differences in the diffraction patterns and output phase maps of the material. This study offers a path to machine learning coupled phase mapping as databases of EBSD patterns encompass an increasing number of the possible space groups, chemistry changes, and lattice parameter variations.

Advanced Ni8W/Ni12W/Ni8W alloy composite substrates used in YBCO-coated conductors with a strong cube texture and high yield strength have been fabricated, and a CeO2 buffer layer film was successfully deposited on the composite substrates. Through in situ tensile testing coupled with electron backscattered diffraction (EBSD) analysis, the stability of the cube texture of Ni8W/Ni12W/Ni8W alloy composite substrates has been investigated. The stress–strain curve shows that the yield strength (at 0.2% strain) of the composite substrates exceeds 250 Mpa. The orientation of grains and boundaries on the surface of the substrates was almost unchanged, while the strain exceeds 0.2%, which indicated that the composite substrates are adequate for depositing buffer layers and YBCO layers by the reel-to-reel process.

The Posada–Asinara Line is a crustal-scale transpressive shear zone affecting the Variscan basement in northern Sardinia during Late Carboniferous time. We investigated a structural transect of the Posada–Asinara Line (Baronie) with the aid of geological mapping and structural analysis. N-verging F2 isoclinal folds with associated mylonitic foliation (S2) are the main deformation features developed during the Posada–Asinara Line activity (D2). The mineral assemblages and microstructures suggest that the Posada–Asinara Line was affected by a retrograde metamorphic path. This is also confirmed by quartz microstructures, where subgrain rotation recrystallization superimposes on grain boundary migration recrystallization. Crystallographic preferred orientation data, obtained using electron backscatter diffraction, allowed analysis of quartz slip systems and estimation of the deformation temperature, vorticity of flow and rheological parameters (flow stress and strain rate) during the Posada–Asinara Line activity. Quartz deformation temperatures of 400 ± 50 °C have been estimated along a transect perpendicular to the Posada–Asinara Line, in agreement with the syn-kinematic post-metamorphic peak mineral assemblages and the late microstructures of quartz. The D2 phase can be subdivided in two events: an early D2early phase, related to the metamorphic peak and low kinematic vorticity (pure shear dominated), and a late D2late phase characterized by a lower metamorphic grade and an increased kinematic vorticity (simple shear dominated). Palaeopiezometry and strain rate estimates associated with the D2late deformation event showed an intensity gradient increasing towards the core of the shear zone. The D2early deformation developed under peak temperature conditions, while the D2late event was active at shallower structural levels.

Surfaces of polycrystalline ferritic Fe–Cr steel with grain sizes of about 13 µm in diameter were investigated with surface sensitive techniques. Thin oxide layers, with a maximum thickness of about 100 nm, were grown by oxidation in air at temperatures up to 450°C and were subsequently characterized using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and atomic force microscopy. Correlative microscopy was applied, which allows for element-specific depth profiles on selected grains with a particular crystal orientation. A strong correlation between the grain orientation and the thickness of the oxide layer was found. The sequence in the oxidation growth rate of ferritic Fe–Cr steel crystal planes is found to be {011} > {111} > {001}, which is unexpectedly opposed to known Fe-based systems. Moreover, for the first time, the Cr/Fe ratio throughout the oxide layer has been determined per grain orientation. A clear order from high to low of {001} > {111} > {011} was detected.