Accuracy assessment of elastic strain measurement by EBSD

Villert, S.; Maurice, Claire; Wyon, C.; Fortunier, Roland

doi:10.1111/j.1365-2818.2009.03120.x

Cited by 122 publications

(96 citation statements)

References 13 publications

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“…The elastic strain contribution to the GND density is often not addressed experimentally, especially in the absence of a quantitative assessment of the significance of the elastic strain contribution to the dislocation density tensor. However, it is significant that in addition to lattice rotation field measurements, advances in the EBSD technique (Wilkinson et al, 2006;Villert et al, 2009;Kacher et al, 2009) have enabled the detection of surface elastic strain fields and the determination of the Kröner dislocation density tensor at surfaces (Wilkinson and Randman, 2010;Britton et al, 2013;Wilkinson et al 2014). …”

Section: Introductionmentioning

confidence: 99%

A statistical analysis of the elastic distortion and dislocation density fields in deformed crystals

Mohamed¹,

Larson²,

Tischler³

et al. 2015

Journal of the Mechanics and Physics of Solids

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CitationA statistical analysis of the elastic distortion and dislocation density fields in deformed crystals This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract.The statistical properties of the elastic distortion fields of dislocations in deforming crystals are investigated using the method of discrete dislocation dynamics to simulate dislocation structures and dislocation density evolution under tensile loading. Probability distribution functions (PDF) and pair correlation functions (PCF) of the simulated internal elastic strains and lattice rotations are generated for tensile strain levels up to 0.85%. The PDFs of simulated lattice rotation are compared with sub-micrometer resolution three-dimensional X-ray microscopy measurements of rotation magnitudes and deformation length scales in 1.0% and 2.3% compression strained Cu single crystals to explore the linkage between experiment and the theoretical analysis. The statistical properties of the deformation simulations are analyzed through determinations of the Nye and Kröner dislocation density tensors. The significance of the magnitudes and the length scales of the elastic strain and the rotation parts of dislocation density tensors are demonstrated, and their relevance to understanding the fundamental aspects of deformation is discussed.

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Section: Introductionmentioning

confidence: 99%

A statistical analysis of the elastic distortion and dislocation density fields in deformed crystals

Mohamed¹,

Larson²,

Tischler³

et al. 2015

Journal of the Mechanics and Physics of Solids

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“…Any error in pattern center calibration propagates into error in the shifts measured by the cross-correlations and results in erroneous measurements of elastic strain and orientation. Indeed, Villert et al have demonstrated that variation in pattern center parameters leads to artificial measurements and increased error [20]. The cross-correlation function is sensitive to sub pixel shifts in the ROIs.…”

Section: Pattern Center Calibrationmentioning

confidence: 98%

Techniques and Applications of the Simulated Pattern Adaptation of Wilkinson’s Method for Advanced Microstructure Analysis and Characterization of Plastic Deformation

et al. 2010

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Electron Backscatter Diffraction (EBSD) based Orientation Imaging Microscopy (OIM) is used routinely at~500 materials laboratories worldwide for the characterization and development of diverse crystalline materials. Statistically significant data sets (~10 7 individual EBSD measurements) can be collected and analyzed within time periods of acceptable beam stability (~10 5 s). However, limitations in angular and spatial resolution have motivated a continued search for more robust EBSD-based methods. Herein is a gathered presentation of advanced techniques in use, intended as a guide to researchers in selecting the most appropriate method for their work. Wilkinson's method has been shown to increase angular resolution nearly two orders of magnitude to ±0.006°, facilitating measurement of elastic strain, lattice curvature, and dislocation density. A simulated pattern adaptation of Wilkinson's method extends these measurement capabilities to polycrystalline materials, by avoiding the need for an experimental strain free reference pattern. The angular resolution limit obtained is~0.04°. Accurate pattern center calibration, essential to the high resolution methods, is accomplished by parallelization of band edges projected onto a sphere centered at the interaction volume. FFT powered cross-correlation functions improve the spatial resolution near grain boundaries and correct for measurement inaccuracies induced by overlapping patterns. To corroborate these claims, exemplary results taken from a wedge-indented nickel single crystal, cold-worked copper polycrystal, and rolled nickel polycrystal are shown.

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“…1), is of great importance in high resolution EBSD work, where the new techniques are much more sensitive to uncertainty in the microscope geometry than earlier EBSD methods. Error in pattern center introduces phantom strains and lattice rotations into absolute strain measurements [5,6]. It can also contribute to error in relative measures (such as deformation gradients) from pattern comparisons when the spatial translation between the compared patterns becomes too great.…”

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confidence: 99%

Advances in High-Resolution EBSD: Extracting Further Details from Kikuchi Patterns

et al. 2011

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Orientation imaging methods have been a mainstay of characterization efforts for crystalline materials for nearly two decades. Electron backscatter diffraction (EBSD) images provide statistical data regarding atomic alignment to create relatively large scale (up to several millimeters) orientation maps in crystalline and polycrystalline materials. However, recent work has highlighted that the information in the diffraction images has generally been under-used. Advances in accessing this often-ignored detail have yielded local strain measurement, improved angular resolution of lattice orientation, mapping of components of dislocation density, and pseudo-symmetry measurement [1][2][3][4].Recent work is presented which adds to these efforts at detail extraction. Similarly to the previously mentioned advances in high resolution EBSD, the work done by the authors relies primarily on cross-correlation and convolution techniques to measure minute differences within the EBSD patterns. These additional developments include: a software-based approach to pattern center determination, with an order of magnitude improvement over the previous methods; mixed pattern separation in polycrystalline materials for greater effective spatial resolution; and work on grain boundary plane determination from surface scans.Precise knowledge of pattern center (PC), the geometry of the electron interaction volume at each scan location in a sample in relation to the phosphor detector screen (Fig. 1), is of great importance in high resolution EBSD work, where the new techniques are much more sensitive to uncertainty in the microscope geometry than earlier EBSD methods. Error in pattern center introduces phantom strains and lattice rotations into absolute strain measurements [5,6]. It can also contribute to error in relative measures (such as deformation gradients) from pattern comparisons when the spatial translation between the compared patterns becomes too great.A software/image processing methodology for determining accurate pattern center for a given EBSD image was previously reported by the authors, based upon analysis of the geometry of the Kikuchi pattern bands (Fig. 2 and Fig. 3). This presentation discusses the PC determination framework, validation procedures undertaken, and applications.Furthermore, EBSD image analysis techniques are applied to the recovery of lattice characteristics of mixed grains within the electron interaction volume as a step towards improving spatial resolution. Monte Carlo simulations of electron backscattering interaction volumes are convolved with simulated grain boundaries and the resulting curves (Fig. 4) are compared with the relative fractions of actual mixed pattern EBSD images in line scans [7]. These comparisons are used to extract three-dimensional grain boundary plane information from an EBSD surface scan. Results are compared with actual 3D data obtained using the focused ion beam (FIB) for material removal [8].

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Accuracy assessment of elastic strain measurement by EBSD

Cited by 122 publications

References 13 publications

A statistical analysis of the elastic distortion and dislocation density fields in deformed crystals

A statistical analysis of the elastic distortion and dislocation density fields in deformed crystals

Techniques and Applications of the Simulated Pattern Adaptation of Wilkinson’s Method for Advanced Microstructure Analysis and Characterization of Plastic Deformation

Advances in High-Resolution EBSD: Extracting Further Details from Kikuchi Patterns

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