Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-53584 Zeitschriftenartikel Winkelmann, A.; Nolze, Gert; Cios, G.; Tokarski, T.; Bala, P.; Hourahine, B.; Trager-Cowan, C. Kikuchi pattern simulations of backscattered and transmitted electrons We discuss a refined simulation approach which treats Kikuchi diffraction patterns in electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). The model considers the result of two combined mechanisms: (a) the dynamical diffraction of electrons emitted coherently from point sources in a crystal and (b) diffraction effects on incoherent diffuse intensity distributions. Using suitable parameter settings, the refined simulation model allows to reproduce various thickness- and energy-dependent features which are observed in experimental Kikuchi diffraction patterns. Excess-deficiency features are treated by the effect of gradients in the incoherent background intensity. Based on the analytical two-beam approximation to dynamical electron diffraction, a phenomenological model of excess-deficiency features is derived, which can be used for pattern matching applications. The model allows to approximate the effect of the incident beam geometry as a correction signal for template patterns which can be reprojected from pre-calculated reference data. As an application, we find that the accuracy of fitted projection centre coordinates in EBSD and TKDcan be affected by changes in the order of 10−3-10−2 if excess-deficiency features are not considered in the theoreticalmodel underlying a best-fit pattern matching approach. Correspondingly, the absolute accuracy of simulation-based EBSD strain determination can suffer frombiases of a similar order of magnitude if excess-deficiency effects are neglected in the simulation model. Wiley Online Library 2021 Journal of Microscopy 284 2 157 184 10.1111/jmi.13051 2021-10-25 OPUS4-53109 Zeitschriftenartikel Winkelmann, A.; Nolze, Gert; Cios, G.; Tokarski, T.; Bala, P.; Hourahine, B.; Trager-Cowan, C. Kikuchi pattern simulations of backscattered and transmitted electrons We discuss a refined simulation approach which treats Kikuchi diffraction patterns in electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). The model considers the result of two combined mechanisms: (a) the dynamical diffraction of electrons emitted coherently from point sources in a crystal and (b) diffraction effects on incoherent diffuse intensity distributions. Using suitable parameter settings, the refined simulation model allows to reproduce various thickness- and energy-dependent features which are observed in experimental Kikuchi diffraction patterns. Excess-deficiency features are treated by the effect of gradients in the incoherent background intensity. Based on the analytical two-beam approximation to dynamical electron diffraction, a phenomenological model of excess-deficiency features is derived, which can be used for pattern matching applications. The model allows to approximate the effect of the incident beam geometry as a correction signal for template patterns which can be reprojected from pre-calculated reference data. As an application, we find that the accuracy of fitted projection centre coordinates in EBSD and TKDcan be affected by changes in the order of 10−3-10-2 if excess-deficiency features are not considered in the theoreticalmodel underlying a best-fit pattern matching approach. Correspondingly, the absolute accuracy of simulation-based EBSD strain determination can suffer frombiases of a similar order of magnitude if excess-deficiency effects are neglected in the simulation model. Wiley Online Library 2021 Journal of Microscopy 284 2 157 184 10.1111/jmi.13051 2021-08-18 OPUS4-53174 Zeitschriftenartikel Tokarski, T.; Nolze, Gert; Winkelmann, A.; Rychlowski, L.; Bala, P.; Cios, G. Transmission Kikuchi diffraction: The impact of the signal-to-noise ratio Signal optimization for transmission Kikuchi diffraction (TKD) measurements in the scanning electron microscope is investigated by a comparison of different sample holder designs. An optimized design is presented, which uses a metal shield to efficiently trap the electron beam after transmission through the sample. For comparison, a second holder configuration allows a significant number of the transmitted electrons to scatter back from the surface of the sample holder onto the diffraction camera screen. It is shown that the secondary interaction with the sample holder leads to a significant increase in the background level, as well as to additional noise in the final Kikuchi diffraction signal. The clean TKD signal of the optimized holder design with reduced background scattering makes it possible to use small signal changes in the range of 2% of the camera full dynamic range. As is shown by an analysis of the power spectrum, the signal-to-noise ratio in the processed Kikuchi diffraction patterns is improved by an order of magnitude. As a result, the optimized design allows an increase in pattern signal to noise ratio which may lead to increase in measurement speed and indexing reliability. Amsterdam Elsevier 2021 Ultramicroscopy 230 1 8 urn:nbn:de:kobv:b43-531743 10.1016/j.ultramic.2021.113372 https://creativecommons.org/licenses/by/4.0/deed.de 2021-09-02 OPUS4-52707 Zeitschriftenartikel Nolze, Gert; Tokarski, T.; Rychlowski, L.; Cios, G.; Winkelmann, A. Crystallographic analysis of the lattice metric (CALM) from single electron backscatter diffraction or transmission Kikuchi diffraction patterns A new software is presented for the determination of crystal lattice parameters from the positions and widths of Kikuchi bands in a diffraction pattern. Starting with a single wide-angle Kikuchi pattern of arbitrary resolution and unknown phase, the traces of all visibly diffracting lattice planes are manually derived from four initial Kikuchi band traces via an intuitive graphical user interface. A single Kikuchi bandwidth is then used as reference to scale all reciprocal lattice point distances. Kikuchi band detection, via a filtered Funk transformation, and simultaneous display of the band intensity profile helps users to select band positions and widths. Bandwidths are calculated using the first derivative of the band profiles as excess-deficiency effects have minimal influence. From the reciprocal lattice, the metrics of possible Bravais lattice types are derived for all crystal systems. The measured lattice parameters achieve a precision of <1%, even for good quality Kikuchi diffraction patterns of 400 x 300 pixels. This band-edge detection approach has been validated on several hundred experimental diffraction patterns from phases of different symmetries and random orientations. It produces a systematic lattice parameter offset of up to ±4%, which appears to scale with the mean atomic number or the backscatter coefficient. 2021 Journal of Applied Crystallography 54 Pt 3 1012 1022 urn:nbn:de:kobv:b43-527076 10.1107/S1600576721004210 https://creativecommons.org/licenses/by/4.0/deed.de 2021-05-31 OPUS4-50934 Zeitschriftenartikel Winkelmann, A.; Nolze, Gert; Cios, G.; Tokarski, T.; Bala, P. Refined Calibration Model for Improving the Orientation Precision of Electron Backscatter Diffraction Maps For the precise determination of orientations in polycrystalline materials, electron backscatter diffraction (EBSD) requires a consistent calibration of the diffraction geometry in the scanning electron microscope (SEM). In the present paper, the variation of the projection center for the Kikuchi diffraction patterns which are measured by EBSD is calibrated using a projective transformation model for the SEM beam scan positions on the sample. Based on a full pattern matching approach between simulated and experimental Kikuchi patterns, individual projection center estimates are determined on a subgrid of the EBSD map, from which least-square fits to affine and projective transformations can be obtained. Reference measurements on single-crystalline silicon are used to quantify the orientation errors which result from different calibration models for the variation of the projection center. MDPI 2020 Materials 13 12 2816 urn:nbn:de:kobv:b43-509342 10.3390/ma13122816 https://creativecommons.org/licenses/by/4.0/deed.de 2020-06-24 OPUS4-51422 Zeitschriftenartikel Cios, G.; Nolze, Gert; Winkelmann, A.; Tokarski, T.; Hielscher, R.; Strzalka, R.; Buganski, I.; Wolny, J.; Bala, P. Approximant-based orientation determination of quasicrystals using electron backscatter diffraction Orientation mapping of quasicrystalline materials is demonstrated using crystalline approximant structures in the technique of electron backscatter diffraction (EBSD). The approximant-based orientations are symmetrised according to the rotational point group of the quasicrystal, including the visualization of orientation maps using proper colour keys for quasicrystal symmetries. Alternatively, approximant-based orientation data can also be treated using pseudosymmetry post-processing options in the EBSD system software, which enables basic grain size estimations. Approximant-based orientation analyses are demonstrated for icosahedral and decagonal quasicrystals. Elsevier B.V. 2020 Ultramicroscopy 218 113093 urn:nbn:de:kobv:b43-514221 10.1016/j.ultramic.2020.113093 https://creativecommons.org/licenses/by/4.0/deed.de 2020-10-14 OPUS4-50762 Zeitschriftenartikel Nolze, Gert; Tokarski, T.; Cios, G.; Winkelmann, A. Manual measurement of angles in backscattered and transmission Kikuchi diffraction patterns A historical tool for crystallographic analysis is provided by the Hilton net, which can be used for manually surveying the crystal lattice as it is manifested by the Kikuchi bands in a gnomonic projection. For a quantitative analysis using the Hilton net, the projection centre as the relative position of the signal source with respect to the detector plane needs to be known. Interplanar angles are accessible with a precision and accuracy which is estimated to be ≤0.3o. Angles between any directions, e.g. zone axes, are directly readable. Finally, for the rare case of an unknown projection-centre position, its determination is demonstrated by adapting an old approach developed for photogrammetric applications. It requires the indexing of four zone axes [uvw]i in a backscattered Kikuchi diffraction pattern of a known phase collected under comparable geometric conditions. 2020 Journal of Applied Crystallography 53 435 443 urn:nbn:de:kobv:b43-507625 10.1107/S1600576720000692 https://creativecommons.org/licenses/by/4.0/deed.de 2020-05-13 OPUS4-50761 Zeitschriftenartikel Winkelmann, A.; Cios, G.; Tokarski, T.; Nolze, Gert; Hielscher, R.; Koziel, T. EBSD orientation analysis based on experimental Kikuchi reference patterns Orientation determination does not necessarily require complete knowledge of the local atomic arrangement in a crystalline phase. We present a method for microstructural phase discrimination and orientation analysis of phases for which there is only limited crystallographic information available. In this method, experimental Kikuchi diffraction patterns are utilized to generate a self-consistent master reference for use in the technique of Electron Backscatter Diffraction (EBSD). The experimentally derived master data serves as an application-specific reference in EBSD pattern matching approaches. As application examples, we map the locally varying orientations in samples of icosahedral quasicrystals observed in a Ti40Zr40Ni20 alloy, and we analyse AlNiCo decagonal quasicrystals. Elsevier Ltd. 2020 Acta Materialia 188 376 385 urn:nbn:de:kobv:b43-507611 10.1016/j.actamat.2020.01.053 https://creativecommons.org/licenses/by/4.0/deed.de 2020-05-13 OPUS4-51907 Forschungsdatensatz Winkelmann, A.; Britton, T. B.; Nolze, Gert EBSD Kikuchi Pattern Analysis, Silicon 15kV Supplementary data and images for Si EBSD pattern analysis as presented in: A. Winkelmann, T.B. Britton, G. Nolze "Constraints on the effective electron energy spectrum in backscatter Kikuchi diffraction", Physical Review B (2019). Geneva Zenodo Bundesanstalt für Materialforschung und -prüfung (BAM) 2019 10.5281/zenodo.2565061 https://creativecommons.org/licenses/by/4.0/deed.de 2020-12-21 OPUS4-52161 Zeitschriftenartikel Nolze, Gert; Winkelmann, A. About the reliability of EBSD measurements: Data enhancement An extensive set of information about the diffracting volume is carried by EBSD patterns: the crystal lattice, the reciprocal lattice, the crystal structure, the crystal symmetry, the mean periodic number of the diffracting phase, the source point from where it has been projected (projection centre), the crystal orientation, the sample topography (local tilt), the (preparation) quality of defect density of the crystal, and possible pattern overlaps. Some of this information is used regularly in conventional EBSD analyses software while others are still waiting for a more widespread application. Despite the wealth of information available, the accuracy and precision of the data that are presently extracted from conventional EBSD patterns are often well below the actual physical limits. Using a selection of example applications, we will demonstrate the gain in angular resolution possible using relatively low-resolution patterns of approximately 20k pixels in combination with pattern matching (PM) approaches. In this way, fine details in a microstructure can be revealed which would otherwise be hidden in the orientation noise. IOP Science 2020 Materials Science and Engineering 891 012018 urn:nbn:de:kobv:b43-521618 10.1088/1757-899X/891/1/012018 https://creativecommons.org/licenses/by/4.0/deed.de 2021-02-25 OPUS4-52343 Zeitschriftenartikel Nolze, Gert; Winkelmann, A.; Cios, G.; Tokarski, T. Tetragonality mapping of martensite in high-carbon steel by EBSD The locally varying tetragonality in martensite grains of a high-carbon steel (1.2 mass percent C) was resolved by electron backscatter diffraction (EBSD) with a spatial resolution in the order of 100 nm. Compared to spatially integrating X-ray diffraction, which yielded an average tetragonality fo c/a=1.05, the EBSD measurements in the scanning electron microscope allowed to image a local variation of the lattice papameter ration c/a in the range of 1.02 ≤ c/a ≤ 1.07. The local variation of tetragonality is confirmed by two different EBSD data analysis approaches based on the fitting of simulated to experimental EBSD patterns. The resulting EBSD-based tetragonality maps are pointing to a complex interaction of carbon concentration and local lattice distortions during the formation process of martensitic structures. Elsevier Inc. 2021 Materials Characterization 175 111040 10.1016/j.matchar.2021.111040 2021-03-29 OPUS4-47296 Zeitschriftenartikel Winkelmann, A.; Nolze, Gert; Cios, G.; Tokarski, T. Mapping of local lattice parameter ratios by projective Kikuchi pattern matching We describe a lattice-based crystallographic approximation for the analysis of distorted crystal structures via Electron Backscatter Diffraction (EBSD) in the scanning electron microscope. EBSD patterns are closely linked to local lattice parameter ratios via Kikuchi bands that indicate geometrical lattice plane projections. Based on the transformation properties of points and lines in the real projective plane, we can obtain continuous estimations of the local lattice distortion based on projectively transformed Kikuchi diffraction simulations for a reference structure. By quantitative image matching to a projective transformation model of the lattice distortion in the full solid angle of possible scattering directions, we enforce a crystallographically consistent approximation in the fitting procedure of distorted simulations to the experimentally observed diffraction patterns. As an application example, we map the locally varying tetragonality in martensite grains of steel. College Park, MD American Physical Society 2018 Physical review materials 2 12 123803, 1 15 10.1103/PhysRevMaterials.2.123803 2019-02-01 OPUS4-47635 Zeitschriftenartikel Nolze, Gert; Winkelmann, A.; Britton, T. B. Constraints on the effective electron energy spectrum in backscatter Kikuchi diffraction Electron backscatter diffraction (EBSD) is a technique to obtain microcrystallographic information from materials by collecting large-angle Kikuchi patterns in the scanning electron microscope (SEM). An important fundamental question concerns the scattering-angle dependent electron energy distribution, which is relevant for the formation of the Kikuchi diffraction patterns. Here we review the existing experimental data and explore the effective energy spectrum that is operative in the generation of backscatter Kikuchi patterns from silicon. We use a full pattern comparison of experimental data with dynamical electron diffraction simulations. Our energy-dependent cross-correlation based pattern matching approach establishes improved constraints on the effective Kikuchi pattern energy spectrum, which is relevant for high-resolution EBSD pattern simulations and their applications. AIP American Physical Society 2019 Physical review B 99 6 064115-1 064115-13 2019-03-29 OPUS4-58158 Zeitschriftenartikel Cios, G.; Winkelmann, A.; Nolze, Gert; Tokarski, T.; Rychlowski, L.; Dan, L.; Bala, P. Mapping of lattice distortion in martensitic steel—Comparison of different evaluation methods of EBSD patterns To visualize the varying tetragonal distortions in high carbon martensitic steels by EBSD, two different approaches have been applied on backscattered Kikuchi diffraction (BKD) patterns. A band-edge refinement technique called Refined Accuracy (RA) (Oxford Instruments) is compared with a technique called Pattern Matching (PM), which optimizes the fit to a simulated BKD signal. RA distinguishes between hypothetical phases of different fixed 𝑐∕𝑎, while PM determines a best fitting continuous 𝑐∕𝑎 by projective transformation of a master pattern. Both techniques require stored BKD patterns. The sensitivity of the 𝑐∕𝑎-determination was tested by investigating the microstructure of a ferritic steel with an expected 𝑐∕𝑎 = 1. The influence of the Kikuchi pattern noise on 𝑐∕𝑎 was compared for a single or 40 averaged frames per measuring point, and turned out to be not significant. The application of RA and PM on the martensitic microstructure delivered qualitatively similar maps of 𝑐∕𝑎. The comparison of RA and PM shows that RA is suitably fast and precise during mapping the martensite 𝑐∕𝑎 ratio in analyses of high carbon martensite, especially for fast initial surveys. As RA leads quantitatively to higher noise in 𝑐∕𝑎, the PM analysis can be used for higher precision results. 2023 Ultramicroscopy 253 1 11 10.1016/j.ultramic.2023.113824 2023-09-06