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The necessary parameters (rotation axis, incident electron beam direction and beam tilt path) in order to describe the diffraction geometry in the Rotation Electron Diffraction (RED) method during data collection are determined and refined. These parameters are prerequisites for the subsequent calculations of excitation errors, sg, for zero (ZOLZ) or higher order Laue zones (HOLZ) reflections. Comparison with simulated results, for a CoP3 thermoelectric crystal, shows excellent agreement between the two approaches -calculated and simulated. In addition to their determination, a thorough refinement methodology for the incident electron beam direction and beam tilt path has been applied, too, based on Kikuchi lines of HOLZ reflections. Incorporation of the refined excitation error values can be considered both in theoretical calculations for diffracted beam intensities, based on the Bloch wave method, as well as in deducing integrated intensities from experimental rocking curves. The methodology described in this study is quite indispensable, as it forms an essential step for performing dynamical calculations in RED, enabling thus enhanced accuracy in structural parameter clarification. The latter is especially important in the case of thermal factors refinement for e.g. thermoelectrics, which are imperative for material properties’ evaluation.

The microstructure and chemical composition of a 316L stainless steel prepared by selective laser melting have been characterized using electron backscatter diffraction, transmission electron microscopy and atom probe tomography (APT). A multi-scale microstructure in the 316L stainless steel was observed in the as-built samples, consisting of equiaxed and columnar grains, dislocation cell blocks, dislocation cells, individual dislocations and nano-sized particles. The misorientations across the dislocation cells were determined based on local crystallographic orientation measurements using a Kikuchi pattern method. The dislocation cells have very small misorientation angles, with an average angle of 0.9°, and are arranged to form dislocation cell-blocks, with cell-block boundary misorientation angles generally larger than 2°. The APT data reveal that alloying elements are evenly distributed in the matrix as well as a high nitrogen content in the as-built material. Based on quantification of the microstructural parameters, good agreement is found between the yield strength as calculated from a linear sum of different strengthening contributions, and the experimentally measured value, with significant contributions both from dislocation strengthening and solid solution strengthening effects.

In this paper an alternative method of off-line Kikuchi pattern centre calibration and orientation mapping, utilising the cross-correlation between entire experimental patterns and dynamical simulated patterns is applied and evaluated. To demonstrate the improvement in angular resolution compared to Hough transform based methods, EBSD datasets of a silicon monocrystal were analysed using both, classical and the presented cross-correlation based method, which revealed significant enhancement of angular resolution for the refined method. The mean misorientation over the monocrystalline sample was found to be up to one order of magnitude lower compared to common methods, with an angular resolution of up to 0.06° indicating a substantial gain in orientation precision. The pattern centres were determined for a number of patterns on the map, using pattern matching refinement as well. Subsequently, a multiple linear regression model was computed to correlate pattern centre positions (XPC, YPC) and detector distances (ZSSD) to x- and y-coordinates on the map by means of plane equations. Employing this method, a reduction of orientation noise was achieved in highly deformed Silicon crystals with large intragranular orientation ranges. Furthermore, it was shown that the cross correlation coefficient CC can be used as a parameter indicating the pattern quality and hence can be utilised to create a pseudo greyscale image of the surface, showing grain boundaries and also depicting lattice distortions.

Automated orientation mapping in SEM, until now relying on EBSD solely, is currently being improved with the development of the TKD technique. As part of the development of TKD, we introduce a new, TEM-like geometric configuration, with a detector "on-axis" relative to the electron beam, while the detector was "off-axis" in its first form. This new technique produces a wide range of diffraction contrast (spots, lines, bands), varying with sample thickness, incident energy, atomic number and scattering angle. Some of the main trends are identified and discussed. In particular, a model based on the plasmon and phonon scattering is proposed to account for the disappearing of diffraction spots with thickness and incident energy. This work should help experimentalists determine which microscope and sample parameters to use in order to obtain a specific contrast. Finally, the strength and weakness of each diffraction feature for orientation mapping are also reviewed.

Angle-resolved electron Rutherford backscattering (ERBS) measurements using an electrostatic electron energy analyser can provide unique access to element-resolved crystallographic information. We present Kikuchi pattern measurements of the non-centrosymmetric crystal GaP, separately resolving the contributions of electrons backscattered from Ga and P. In comparison to element-integrated measurements like in the method of electron backscatter diffraction (EBSD), the effect of the absence of a proper 4-fold rotation axis in the point group of GaP can be sensed with a much higher visibility via the element-resolved Ga to P intensity ratio. These element-resolved measurements make it possible to experimentally attribute the previously observed point-group dependent effect in element-integrated EBSD measurements to the larger contribution of electrons scattered from Ga compared to P.

Modern scanning electron microscopes (SEM) equipped with thermally assisted field emission guns (Schottky FEG) are capable of imaging with a resolution in the range of several nanometers or better. Simultaneously, the high electron beam current can be used, which enables fast chemical and crystallographic analysis with a higher resolution than is normally offered by SEM with a tungsten cathode. The current resolution that limits the EDS and EBSD analysis is related to materials' physics, particularly to the electron-specimen interaction volume. The application of thin, electron-transparent specimens, instead of bulk samples, improves the resolution and allows for the detailed analysis of very fine microstructural features. Beside the typical imaging mode, it is possible to use a standard EBSD camera in such a configuration that only transmitted and scattered electrons are detected. This modern approach was successfully applied to various materials giving rise to significant resolution improvement, especially for the light element magnesium based alloys. This paper presents an insight into the application of the transmission Kikuchi diffraction (TKD) technique applied to the most troublesome, heavily-deformed materials. In particular, the values of the highest possible acquisition rates for high resolution and high quality mapping were estimated within typical imaging conditions of stainless steel and magnesium-yttrium alloy.

The crystal growth of large high-quality inclusion-free CdWO4 crystals, 110 mm in diameter and mass up to 20 kg, has been carried out by the Low Thermal Gradient Czochralski (LTG Cz) technique. The high-purity CdWO 4 (010) surface has been prepared by cleavage and high structural quality of the surface has been verified by RHEED, revealing a system of Kikuchi lines. The chemical state and electronic structure of the surface have been studied using X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). The total and partial densities of states of the CdWO 4 tungstate were calculated employing the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The results indicate that the principal contributors to the valence band of CdWO 4 are the Cd 4 d , W 5 d and O 2 p states which contribute mainly at the bottom, in the central portion and at the top of the valence band, respectively, with also significant contributions of the mentioned states throughout the whole CdWO 4 valence-band region. With respect to the occupation of the O 2 p states, the results of the FP-LAPW calculations are confirmed by comparison on a common energy scale of the XPS valence-band spectrum and the XES band representing the energy distribution of the O 2 p states in this compound. Additionally, the FP-LAPW data allow us to conclude that the CdWO 4 tungstate is a non-direct semiconductor.

We demonstrate an approach to overcome Kikuchi pattern misindexing problems caused by crystallographic pseudosymmetry in electron backscatter diffraction (EBSD) measurements. Based on the quantitative comparison of experimentally measured Kikuchi patterns with dynamical electron diffraction simulations, the algorithm identifies the best-fit orientation from a set of pseudosymmetric candidates. Using measurements on framboidal pyrite (FeS2) as an example, we also show the improvement of the orientation precision using this approach.

The kinetic energy of keV electrons backscattered from a rutile (TiO2) surface depends measurably on the mass of the scattering atom. This makes it possible to determine separately the angular distribution of electrons backscattered elastically from either Ti or O. Diffraction effects of these backscattered electrons inside the rutile crystal lead to the formation of Kikuchi patterns. The element-resolved Kikuchi patterns of Ti and O differ characteristically, but each can be described fairly well in terms of the dynamical theory of diffraction. Qualitatively, much of the differences can be understood by considering the relative arrangement of the Ti and O atoms with respect to planes defined by the crystal lattice.

It was previously found that peritectic-forming solutes are more favourable for the grain refinement of cast Al alloys than eutectic-forming solutes. In this work, we report that the eutectic-forming solute, Mg, can also significantly grain refine cast Zn. Differential thermal analysis (DTA) of a Zn-Mg alloy, in which efficient grain refinement occurred, evidenced an unexpected peak that appeared before the nucleation of η-Zn grains on the DTA spectrum. Based on extensive examination using X-ray diffraction, high resolution SEM and EDS, it was found that: (a) some faceted Zn-Mg intermetallic particles were reproducibly observed; (b) the particles were located at or near grain centres; (c) the atomic ratio of Mg to Zn in the intermetallic compound was determined to be around 1/2. Using tilting selected area diffraction (SAD) and convergent beam Kikuchi line diffraction pattern (CBKLDP) techniques, these faceted particles were identified as MgZn 2 and an orientation relationship between such grain-centred MgZn 2 particles and the η-Zn matrix was determined. Hence, the unexpected peak on the DTA spectrum is believed to correspond to the formation of MgZn 2 particles, which act as effective heterogeneous nucleation sites in the alloy. Together with the effect of Mg solute on restricting grain growth, such heterogeneous nucleation is cooperatively responsible for the grain size reduction in Zn-Mg alloys.

We present a study of the efficiency of the utility of scanning electron microscope (SEM)-based transmission methods for characterizing grain structure in thinned bulk metals. Foils of type 316 stainless steel were prepared by two methods commonly used for transmission electron microscopy — double-jet electropolishing and focused ion beam milling. A customized holder allowed positioning of the foils in a configuration appropriate for both transmission electron forward scatter diffraction, and for transmission imaging by the use of a forescatter detector with two diodes. We found that both crystallographic orientation maps and dark-field transmitted images could be obtained for specimens prepared by either method. However, for both methods, preparation-induced artifacts may affect the quality or accuracy of transmission SEM data, especially those acquired by the use of transmission Kikuchi diffraction. Generally, the quality of orientation data was better for specimens prepared by electropolishing, due to the absence of ion-induced damage.

We demonstrate the determination of crystal chirality using electron backscatter diffraction (EBSD) in the scanning electron microscope. The chirality of α-quartz as a space-group-dependent property is verified via direct comparison of experimental diffraction features to simulations using the dynamical theory of electron diffraction.

A texture and orientation study was performed on the hard turning layers by utilizing newly developed Transmission Kikuchi Diffraction technique complemented by glancing angle X-ray diffraction and high resolution transmission electron microscopy (HRTEM). Results indicate that the hard turning process transforms the typical martensite lath/plate structure into equiaxed grains with low angle (

Centimeter-sized optical quality plate-like PbB 4 O 7 crystals have been grown by Czochralski method. The fundamental absorption edge has been found at 237 nm (corresponding bandgap 5.75 eV) with the distinct sideband protruding up to 300 nm. The crystals are well faceted with the (1 0 0), (0 1 0) and (1 0 1) planes, (1 0 0) surfaces being mostly developed. The etching in diluted nitric acid (5 wt.%) at the temperature of 90 °C have been used to reveal the defect structure and remove melt residuals. The (1 0 0) surface shows the presence of etching pits and twin boundaries. The Kikuchi line pattern and developed microrelief with the roughness of ∼8 nm have been observed by RHEED and AFM, respectively.

The effect of transition elements on grain refinement of 7475 aluminum alloy sheets produced by warm rolling was investigated. The alloy which contains zirconium instead of chromium showed ultra fine structures with stable subgrains after warm rolling at 350 °C, followed by solution heat treatment at 480 °C. The average subgrain diameter was approximately 3 μm. It became clear that zirconium in solution has the effect of stabilizing subgrains due to precipitation of fine Al3Zr compounds during warm rolling. On the other hand, chromium-bearing compounds precipitate before warm rolling and they grow up to relatively large size during warm rolling. The warm rolled sheets with fine subgrains have unique properties compared with conventional 7475 aluminum alloy sheets produced by cold rolling. The warm rolled sheets solution heat treated had subgrain structures through the thickness with a high proportion of low-angle boundary less than 15°. The strength of the warm rolled sheets in T6 condition was about 10% higher than that of conventional 7475 aluminum alloy sheets. As the most remarkable point in the warm rolled sheets, the high Lankford (r) value of 3.5 was measured in the orientation of 45° to rolling direction, with the average r-value of 2.2. The high r-value would be derived from well developed β-fiber textures, especially with the strong {011}«211» brass component. The warm rolled sheets also had high resistance to SCC. From Kikuchi lines analysis and TEM images, it was found that PFZs were hardly formed along the low-angle boundaries of the warm rolled sheets in T6 condition. This would be a factor to lead to the improvement of resistance to SCC because of reducing the difference in electrochemical property between the grain boundary area and the grain interior.

Quantitative analysis was performed for electron channeling contrast (ECC) of dislocations in a [001] single-crystal 316 L stainless steel sample in order to establish the range of deviation parameter, w, for optimal dislocation imaging. Channeling contrast was evaluated from a series of ECC images taken as a function of sample tilt at ∼ 0.1° increments across 〈200〉 Kikuchi lines. The deviation parameter, w, was estimated by quantitative analysis of several parameters, namely experimental dislocation contrast intensity and dislocation feature width, as well as calculated BSE signal. Our analysis reveals that optimum dislocation imaging conditions by ECC occur for positive values of w. Under these imaging conditions, dislocations displayed strong contrast and narrow dislocation feature width, y. In particular, we found that the value of y can be greatly reduced (about two times in the present work) by using large positive values of w (w > 1.0 ± 0.5). Out of these channeling conditions, dislocations displayed weak contrast and larger y-values were measured.

A polycrystalline Cu of 99.995% purity has been deformed by dynamic plastic deformation at liquid nitrogen temperature to a strain of 2.1 (LNT-DPD Cu). Three distinct regions that are dominated by dislocation slip, shear banding and nanotwinning, form a multi-component nanostructure. The microstructure of each region has been quantified by transmission electron microscopy assisted by Kikuchi line analysis. Based on the structural parameters the stored energy of each region was evaluated, and the total energy can be assumed to be a linear additivity of that in each region weighted by the respective volume fraction. A microstructure based evaluation of the stored energy of multi-component nanostructure has been proposed.

Orientation microscopy of polycrystalline materials has developed, within a few years, into an invaluable tool of materials science and geology. It is based on backscatter electron diffraction in the Scanning Electron Microscope. Individual grain orientations are conveniently measured by analysing backscatter Kikuchi patterns, either interactively or fully automatically. A straightforward method of noise reduction is presented which significantly improves the quality of Kikuchi patterns for analysis. The image is not filtered in real image domain, but peaks in the Radon domain are accentuated by applying an intensity enhancement operator, so automated band detection is performed more reliably. A cleansed Kikuchi pattern can be constructed, for visual inspection, by an inverse Radon transform. Experimental results are presented.

The application of convergent beam electron diffraction (CBED) to determine symmetry, refine structure factors, and measure specimen thickness requires rather thick specimen and is very difficult or even impossible in the case of large unit cell materials. The large-angle rocking-beam electron diffraction (LARBED) technique introduced in this paper gives access to the kind of experimental data contained in CBED patterns but over a much larger angular range. In addition to symmetry determination and thickness measurement even for thin samples this technique also allows, in principle, very accurate measurements of structure factors. Similar to precession electron diffraction (PED), LARBED uses the illumination tilt coils to sequentially change the angle of incidence of the electron beam over a very large range. I will present results obtained by a recently developed self-calibrating acquisition software which compensates for aberration-induced probe shifts during the acquisition of LARBED patterns and keeps the probe within a few nm, while covering a tilt range from 0 to 100 mrad. This paper is dedicated to Prof. John C. H. Spence on the occasion of his 65th birthday.

Shear plastic deformation in ECAP occurs through the formation, movement and storage of dislocations. The differences which exist between shearing characteristics lead to important implications concerning the optimum processing route. It is known that the effectiveness of cell evolution into an array of high-angle boundaries (HABs) is in the order BC > C > A, or A > BC > C, depending on the two-channel-angle intersection of the ECAP die. In route A, large portions of HABs are continuously and progressively generated, while routes C and BC cause fully redundant deformation at each 2n passes, and each 4n passes, respectively. This study is focused on dislocation generation, storage and recombination during ECAP for routes A, C and BC. Kikuchi bands identified with TEM were used to quantitatively measure the cell and grain boundary misorientation. ECAP was performed on an AA1200 commercially pure aluminium alloy up to e = 8.64. A different hierarchy for HAB generation efficiency was found. Thermal stability was studied by annealing the alloy at 0.5, 0.6, 0.7 TM (where TM is the alloy melting point) for 2 h after the severe plastic deformation. It appeared that, even if route BC involves the fastest microstructure grain refining, route C is likely to be the most stable upon reheating.

In Electron Rutherford Backscattering Spectroscopy (ERBS) energetic electrons (in our case up to 40 keV) impinge on a target and one measures the energy of elastically scattered electrons. This energy depends on the mass of the scattering atom, due to the recoil effect. This technique thus provides information about the sample composition. For single crystals the interaction of the projectile electron with the crystal potential modifies the angular intensity distribution of the scattered electrons. This leads, for example, to the well-known Kikuchi patterns. Here we investigate if such modified angular distribution has any influence on the intensity ratio of the observed elastic peaks in ERBS. Dramatic effects are found. Implications of these observations for quantitative surface analysis using energetic electrons are discussed.

The analysis of the achieved texture is of great importance for the performance of ferrite materials, either bulk or thin films. The recently developed electron backscatter diffraction (EBSD) technique enables a spatially resolved study of the crystallographic orientations by means of recording of Kikuchi patterns. To our knowledge, such a thorough EBSD analysis was not yet performed in any oxidic magnetic material, and only very recently on magnetite thin films by us. A good surface polishing/cleaning is essential for this analysis, as the method requires an undisturbed surface area for a high image quality (IQ). This information is recorded to each measured Kikuchi pattern, together with a parameter describing the quality of indexation. Here, the spatially highly resolved EBSD mappings provide additional information as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, an analysis of the grain aspect ratio is possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.

We analyze the contrast reversal of Kikuchi bands that can be seen in electron backscatter diffraction (EBSD) patterns under specific experimental conditions. The observed effect can be reproduced using dynamical electron diffraction calculations. Two crucial contributions are identified to be at work: First, the incident beam creates a depth distribution of incoherently backscattered electrons which depends on the incidence angle of the beam. Second, the localized inelastic scattering in the outgoing path leads to pronounced anomalous absorption effects for electrons at grazing emission angles, as these electrons have to go through the largest amount of material. We use simple model depth distributions to account for the incident beam effect, and we assume an exit angle dependent effective crystal thickness in the dynamical electron diffraction calculations. Very good agreement is obtained with experimental observations for silicon at 20keV primary beam energy.

Diffraction patterns of backscattered electrons can provide important crystallographic information with high spatial resolution. Recently, the dynamical theory of electron diffraction was applied to reproduce in great detail backscattering patterns observed in the scanning electron microscope (SEM). However, a fully quantitative comparison of theory and experiment requires angle-resolved measurements of the intensity and the energy of the backscattered electrons, which is difficult to realize in an SEM. This paper determines diffraction patterns of backscattered electrons using an electrostatic analyzer, operating at energies up to 40 keV with sub-eV energy resolution. Measurements are done for different measurement geometries and incoming energies. Generally a good agreement is found between theory and experiment. This spectrometer also allows us to test the influence of the energy loss of the detected electron on the backscattered electron diffraction pattern. It is found that the amplitude of the intensity variation decreases only slowly with increasing energy loss from 0 to 60 eV.

Abalone shell comprises a bio-composite material, combining the properties of inorganic calcite intergrown with organic nacre. This paper reports about the microstructure of this composite. By examining the Kikuchi patterns obtained for nacre (Haliotis discus hannai) using transmission electron microscopy, we have shown that the tiles within nacre have specific orientations. The stereographic projection spheres for the tiles of nacre can be divided into two main types, namely a right oriented region and a left oriented region with respect to the c axis as a reference plane (001). The cluster character of nacre can be explained in terms of the growth mechanism of the ‘Christmas tree’ pattern. The orientation of the c-axis in the nacreous layer is elucidated for the first time. We demonstrate the use of the soluble protein obtained from the tiles of nacre in in vitro calcium carbonate crystallization.

Dislocation structures in deformed metals have been analyzed quantitatively by transmission electron microscopy, high-resolution electron microscopy and Kikuchi line analysis. A general pattern for the microstructural evolution with increasing strain has been established and structural parameters have been defined and quantified. It has been found that two dislocation patterns co-exist in all grains, however, with very different characteristics dependent on grain orientation. This correlation with the grain orientation has been applied in modeling of the tensile flow stress and the flow stress anisotropy of fcc polycrystals. In conclusion some future research areas are briefly outlined.

Commercial purity Al was severely deformed by equal channel angular pressing (ECAP) up to eight passes using route BC. The deformation microstructure was characterized quantitatively by electron-backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The microstructural homogeneity was investigated by EBSD at various locations from center to surface of the samples on a longitudinal section parallel to the pressing direction. Structural parameters including mean boundary spacing, boundary misorientation angle and fraction of high angle grain boundaries were measured and characterized through the section of the ECAP samples. EBSD scans revealed a homogeneous ultrafine grained microstructure after 8 passes. The analysis showed that the fraction of high angle grain boundaries was more than 70% at most locations of the sample section. Also, an average boundary spacing of 380 nm was obtained by the linear intercept method. TEM analysis was used for more detailed characterization of the microstructure, such as low angle boundaries with misorientation angles smaller than 2°. Using the structural parameters–flow stress relationship, the flow stress was estimated based on the EBSD and TEM/Kikuchi-line analyses and compared with measured values.

Bonded silicon-on-insulator (SOI) materials via the Smart-cut^T^M (or ion-cut) process attract increasing interests due to their great capability and versatility in fabricating novel virtual substrates. Previously we reported the successful fabrication of silicon-on-aluminum-nitride (SOAN) structure with smart-cut process [C.L. Men, Z. Xu, Z. An, X.Y. Xie, M. Zhang, C.L. Lin, Physica B 324 (2002) 229]. In this work, we characterize the bonded SOAN structure with Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM) together with Kikuchi line diffraction patterns, and high resolution X-ray diffraction (HRXRD) techniques. It is found that, after smart-cut process, the top Si layer preserves a rather good single crystalline quality, while strain is induced in top Si and can be altered in the annealing step. The rotational misalignment during bonding step can be evaluated by Kikuchi line patterns. Our discussions here may be common for all bonded virtual substrates via smart-cut technology.

Microstructures and martensitic transformation behavior have been examined as for CoNiGa ferromagnetic shape memory alloy (FMSMA) ribbons rapidly solidified by a single-roll melt spinning. Transmission electron microscopy (TEM) bright-field images revealed dense striations in the martensite variants. These striations are identified to be thin twins, as in other FMSMAs. The analysis of a pair of Kikuchi lines in a selected-area electron diffraction pattern indicates that the b / a and c / a axial ratios of the orthorhombic martensite are 1.01 and 0.961, respectively. Crossings of fully twinned martensite variants are frequently observed in the TEM bright-field images, and the internal twins disappear in the crossing regions, that is, the regions are subjected to detwinning. In addition to the crossing of martensite variants, checkers and straight bands of martensite variants are observed in the crystal grains of the ribbon surface. These typical morphologies are supposed to be caused by some self-accommodation of martensitic transformation stress.

The thin sheets of calcite, termed folia, that make up much of the shell of an oyster are composed of foliated lath. Folia of the giant Pacific oyster (Crassostrea gigas) were examined using TEM (transmission electron microscopy) and tested using microindentation and nanoindentation techniques. Analysis of the Kikuchi patterns obtained from the folia showed that there are two types (type I and type II) of preferred orientation, with an angle of around 70° between them. Nanoindentation tests showed that the folia exhibit a hardness of about 3 GPa and elastic modulus of about 73 GPa. Microcracks were generated using a microindenter in order to study the fracture mechanisms of the folia. Following on from these investigations, fracture mechanisms are discussed in conjunction with the correlation between preferred orientation and structural characteristics during cracking of the folia. Comparing the morphology and the polymorphism with nacre (also known as mother of pearl), the advantages of the relatively fast crystal growth and less amount of organic matrix in folia may have interesting implications for the development of sophisticated synthetic materials.

The structure of (1 1 0) plane of Cr-doped CdTe single crystals has been studied by reflection high energy electron diffraction and scanning electron microscopy. Diffraction patterns consist of diffraction spots and Kikuchi lines. However, for very small incident angle, the Debye rings are observed. The constant lattice attributed to these rings is 0.8% less then for pure CdTe. These anomalous properties of the near surface layer are likely to occur due to the concentration of Cr atoms creating compressive surface strains or the effect of crystal cleavage.

The convergent beam Kikuchi line diffraction technique has been used to accurately determine the orientation relationships between bainitic ferrite and retained austenite in a hard bainitic steel. A reproducible orientation relationship has been uniquely observed for both the upper and lower bainite. It is [GRAPHICS] However, the habit plane of upper bainite is different from that of lower bainite. The former has habit plane that is either within 5 degrees of (221)(A) or of (259)(A). The latter only corresponds with a habit plane that is within 5 degrees of (259)(A). The determined orientation relationship is completely consistent with reported results determined using the same technique with an accuracy of +/- 0.5 degrees in lath martensite in an Fe-20 wt.% Ni-6 wt.% Mn alloy and in a low carbon low alloy steel. It also agrees well with the orientation relationship between granular bainite and austenite in an Fe-19 wt.% Ni-3.5 wt.% Mn-0.15 wt.% C steel. Hence it is believed that, at least from a crystallographic point view, the bainite transformation has the characteristics of martensitic transformation. (c) 2006 Elsevier B.V. All rights reserved.

The orientation relationship (OR) between the beta(Zn) phase and the alpha(Al) phase and the corresponding habit planes in a Zn-Al eutectoid alloy were accurately determined using convergent beam Kikuchi line diffraction patterns. In addition to the previously reported OR. [11 (2) over bar0](beta)parallel to[110](alpha), (0002)(beta)parallel to ((1) over bar 11)alpha, two new ORs were observed. They are: [11 (2) over bar0](beta)parallel to [110], ((1) over bar 101)(beta) 0.82 degrees from (002)(alpha) and [(1) over bar 100](beta)parallel to[112](alpha), (0002)(beta) 4.5 degrees from (111)(alpha). These ORs can be explained and understood using the recently developed edge-to-edge matching model. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A new method for unambiguous differentiation and orientation determination of six γ variants and α 2 phase in a two phase TiAl base alloy is presented. The approach involves automatic collection of transmission electron microscopy (TEM) Kikuchi patterns by a digital CCD camera at regular distance of nano steps through nanoprobe scanning. The Kikuchi patterns corresponding to various γ variants and α 2 phase were distinguished through superlattice bands. The procedure is compared with other methods for identification of six γ variants and α 2 phase in terms of their spatial and angular resolutions as well as easiness and rapidity for large data collection. As an example, the technique is utilised to characterise the lamellar structures of a Ti–48(at.%)Al–2Cr–2Nb alloy resulting from heat treatment at high temperature α domain followed by furnace cooling. Each lamella is labelled with its respective γ variant or α 2 phase. The frequencies of the γ and γ / γ interfaces were determined. Moreover, it is noticed that some of the 0° and 180° γ / γ interfaces are in fact semi-coherent, and present a slight deviation from their ideal misorientation.

The microstructure in the electroformed copper liners of shaped charges prepared with different electrolytes was studied by Scanning Electron Microscopy (SEM) and Electron Backscattering Kikuchi Pattern (EBSP) methods. SEM observations revealed the existence of columnar grains in electroformed copper liners of shaped charges formed by electrolyte without any additive and the average grain size is about 3 μm. When an additive is introduced to the electrolyte, the grains formed in the copper liners become equiaxed and finer. EBSP results show that the columnar grain grown during electroformation has the most preferential growth direction, whereas a micro-texture does not exit in the specimen prepared by electrolyte with the additive. Further, explosive detonation deformation experiments show that penetration depth is dramatically improved when the electroformed copper liners of shaped charges exhibit equiaxed grains.

Variant selection of intergranular bcc-Cr precipitates in a Ni–43 mass% Cr alloy was studied by electron backscattering diffraction (EBSD) in a scanning electron microscope equipped with a field emission gun (FESEM) and Kikuchi line analysis in transmission electron microscope (TEM). A single variant was invariably selected at the underlying grain boundaries (GB) when GB-precipitates were KS-related with respect to both the adjacent matrix grains. Meanwhile multiple variants were formed at the GB when GB-precipitates were KS-related to one of the adjacent matrix grains. Theses variant selections were examined with the tilt angle to underlying GB of low-energy interphase boundaries and the orientation relationship with respect to both the adjacent matrix grains. The underlying mechanism was discussed from the viewpoint of activation energy for nucleation of two-dimensional nuclei.

GaCrN-based ferromagnet/nonmagnet/ferromagnet trilayer structures were grown by radio frequency molecular beam epitaxy. During GaN and GaCrN growth, reflection high-energy electron diffraction pattern showed thin streaks and Kikuchi lines, indicating surface flatness and high crystalline quality. Clear hysteresis and saturation characteristics were observed in the magnetization versus magnetic field curves at all the measuring temperatures. The coercivity H c was about 130 Oe at 10 K. Step-like hysteresis loops were also observed at 10 and 300 K because of different Cr concentrations in the two GaCrN layers. Photoluminescence emission was observed from GaCrN. Hysteresis loop was observed in the magnetic field dependence of vertical electrical resistance.

Epitaxially deposited thin films of InAs on semi-insulating GaAs substrates are commonly used for high-speed electronic devices. Large (7%) lattice mismatch between InAs and GaAs leads to Stranski–Krastanov growth mode with formation of 3D islands. The effect of growth temperature in MOVPE deposition, on InAs crystal microstructure was studied. The origin of multiple tilting of the InAs crystal lattice observed for the high temperature growths was investigated in detail. The microstructure of uncoalesced InAs islands was determined using X-ray diffraction rocking curve scans and backscattered electron Kikuchi pattern crystal orientation imaging. Misoriented grains are formed within uncoalesced InAs islands at an early stage during the growth.

The texture and phase distribution of melt-textured YBa 2 Cu 3 O x (YBCO) was studied by means of automated electron backscatter diffraction (EBSD) analysis as a function of the position in the bulk pellet of 4 cm diameter. A total of five samples was cut from the pellet; four samples from the surface of the bulk with different distances to the seed crystal, and one cut in vertical direction in the middle of the pellet. The melt-textured YBCO samples require a two-phase analysis to be performed, so a high surface quality is necessary to enable an automated EBSD scan. Good quality Kikuchi patterns are obtained from both the 1 2 3 and 2 1 1 phases. We found an inhomogeneous distribution of the 2 1 1 particles. Whereas the samples cut from the surface contain a large amount of 2 1 1 particles, in the samples of the vertical direction only traces of 2 1 1 particles are found. Furthermore, we measured the misorientation angle distribution of all samples. The data are presented in form of phase mappings, misorientation distribution functions and pole figures.

Precursor films are deposited on SrTiO 3 single crystals at room temperature by the co-evaporation technique using Y, BaF 2 and Cu as evaporation sources. Then, the precursor films are annealed in a low-pressure oxygen atmosphere without introduction of water vapor. A sample with a reflection high-energy electron diffraction (RHEED) pattern exhibiting some streaks, Kikuchi lines and Kikuchi zone, which resembles that of a single crystal, is successfully prepared. According to the cross-sectional TEM observation results, epitaxial growth of this YBCO film is achieved for the entire film thickness. The transport properties are measured using a small bridge with a width of 0.1 mm and a length of 1 mm by a standard four-probe method. The obtained YBCO film has a high J c of over 1 MA/cm 2 at 77 K and a self-field. Furthermore, we discuss the relationship between the epitaxial YBCO layer thickness and the annealing conditions. Approximately 300- and 400-nm-thick epitaxial YBCO films are successfully prepared.

The dependence of flow stress (measured by tensile experiment) on the microstructure is discussed based on the Hall–Petch (H–P) relationship in interstitial-free steel cold-rolled to different reductions of 10–90%. The microstructure was characterized by TEM with semi-automated Kikuchi pattern analysis method. The significant effect of misorientation on the flow stress was found experimentally. The linear dependence of the slope of H–P relation on the average sub(grain) boundary misorientation is derived based on the work hardening dislocation mechanism. The modified H–P relation, i.e. σ f = σ 0 + K H (( θ av /15)/ d subgrain ) 0.5 is proposed to describe the effect of average misorientation on flow stress.

Transmission electron microscopy observations of the recovered slugs of electroformed copper liner materials that had undergone high-strain-rate deformation show the existence of a wide range of crystal defects, including vacancy clusters and porosity. Cellular structures formed by tangled dislocations and subgrain boundaries consisting of dislocation arrays were also detected. Electron backscattering Kikuchi pattern technique analysis reveals that the fibrous texture observed in the as-formed copper liners of shaped charges disappeared after explosive detonation deformation. In a specimen that had been plastically deformed at a normal strain rate (4×10 −4 s −1 ), a high density of dislocations was observed within grains. These experimental results indicate that dynamic recovery and recrystallization play an important role during high-strain-rate deformation by virtue of a temperature increase in the deformation process, whereas the conventional slip mechanism operates during deformation at the normal strain rates.

W delta doping in Si epitaxial growth by WF 6 and SiH 4 reaction has been investigated using an ultraclean cold-wall low-pressure chemical vapor deposition (CVD) system. Atomic-layer order W deposition is performed on wet-cleaned Si(1 0 0) substrate at 100°C using WF 5 and SiH 4 . Si epitaxial growth is achieved by SiH 4 reaction at 480°C on 4 × 10 13 cm -2 W deposited Si( 1 0 0), however, it is found that almost all the deposited W atoms segregate on the deposited Si film. It is also found that such segregation is suppressed by the atomic-order W diffusion into Si(1 0 0) substrate by the heat treatment at 520 C before the Si deposition. In the case of the Si film deposited on the 1.3 x 10 14 cm 2 W diffused Si, the reflection high-energy electron diffraction (RHEED) pattern indicates the crystallinity and the roughness degrade. In the case of the Si film deposited on the 5 x 10 13 cm -2 W diffused Si, the RHEED pattern shows streaks with Kikuchi lines. As a result, the W delta doping in the Si epitaxial growth is achieved, in which the W concentration is as high as 6 x 10 20 cm -3 and the incorporated W atoms is confined within 2 nm-thick region.

Orientation relationships between Mg24Y5 precipitates and matrix in a Mg-Y alloy were accurately determined using Kikuchi line diffraction. The Burgers relationship with habit planes of {10 (1) over bar0}(H) and {31 (4) over bar0}(H) were observed for all precipitates. Compared with the Mg17Al12 precipitate in AZ91, the precipitation hardening effect in this alloy was significantly increased. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

By means of orientation imaging microscopy, we have investigated grain orientation distributions of various BaTiO3 ceramic samples prepared using different preparation routes. We present details of the required surface preparation steps in order to enable an automated orientation mapping. The samples are characterized by image quality (IQ), grain size (GS) and grain orientation (IPF) maps. Finally, the grain orientation distribution functions are obtained from the measured data. It is shown that the samples do not exhibit any preferred grain orientations.

A model for stress-induced martensitic transformation, which was successfully used in an Fe-Ni-C alloy in compression conditions, has been further studied and extended to investigate the stress-induced martensitic transformation in Fe-Ni-C alloy in tension and a white cast iron in compression. The predicted relationship between the bulk specimen volume change and the fraction of martensite formed has been experimentally proved. The model also predicts which orientation of grains should transform first and the predictions have also been experimentally confirmed using convergent beam Kikuchi line diffraction. (C) 2002 Elsevier Science B.V. All rights reserved.

Aluminum deposit was produced by cold gas dynamic spraying technique. Due to the severe plastic deformation resulted from high speed impact, the spherical particles were deformed to be elongated splats. The microstructure of tangled area with interlaced thin strips was found at the outmost surface of particles, which contributes to the mechanical interlocking between particles. The microstructure evolution from the lamellar microbands with elongated subgrains to the newly formed refined area was observed at the region of particle boundaries. Corresponding to the various deformation conditions, such as nonuniform strain and geometrical effect, it shows a mixture of low and high angle boundaries between adjacent grains along the particle boundary, measured by convergent beam Kikuchi line diffraction.

Unusual reflection high-energy electron diffraction (RHEED) patterns were obtained on a homoepitaxial diamond (001) surface. A RHEED pattern with only Kikuchi patterns was observed on the [010] direction, while a RHEED pattern with the specular point missing was observed on the 0 1 0 direction, the opposite azimuth angle. In the [100] direction, perpendicular to the above azimuth angles, a RHEED pattern with the 040-0 4 0 Kikuchi band tilting from the normal angle to the horizontal shadow edge-line was observed. These patterns are explained by the surface tilt, as in an echelette grating. The off-angle of the surface was estimated to be 3° from the RHEED patterns. This study shows that RHEED is a powerful method for the simultaneous estimation of the surface structures, roughness, and tilt.

We propose all the diffraction patterns can be directly transformed to provide three-dimensional atomic structures for the system studied. Depending on the scattering process, either the holography or Patterson transform scheme is used. For diffraction patterns which are generated from a localized emitter source or dominated by an inelastic-scattering feature like core-level photoelectron or low-energy Kikuchi electron, holography transform is needed. On the other hand, for diffraction patterns which were dominated by elastic-scattering, like grazing-incidence X-ray diffraction, electron correlated thermal diffuse scattering or low-energy electron diffraction curves, Patterson transform is needed. To prove our point, high-fidelity and artifact-free three-dimensional atomic structures obtained by transform of low-energy Kikuchi electron patterns and low-energy electron diffraction curves are presented. The future of these direct methods by transforming diffraction patterns will be discussed.

The internal structure of planar dislocation boundaries is explored through a coupling of experimental observations of extended geometrically necessary boundaries (GNBs) in deformed single crystals with a dislocation dynamics simulation. The internal dislocation structure of a GNB is approached first through standard diffraction contrast analyses to identify the boundary Burgers vectors in the transmission electron microscope (TEM). This result is placed in the context of a large series of boundaries by the calculation of boundary misorientation angle/axis pairs from Kikuchi pattern analysis in the TEM of orientations on either side of the boundaries. Of special interest are the boundary misorientation axes which together with the boundary normal, allow one to estimate the contribution of primary and secondary dislocations to boundary rotations. Selected boundaries are constructed using the experimental data, crystal plasticity analysis and Frank’s formula. The constructed boundaries are input into the dislocation dynamics code and allowed to equilibrate (relax). The internal stress field of the boundary is determined.