Orientation Precision of Electron Backscatter Diffraction Measurements Near Grain Boundaries

Wright, Stuart I.; Nowell, Matthew M.; Kloe, René de; Chan, Lisa

doi:10.1017/s143192761400035x

Cited by 44 publications

(28 citation statements)

References 23 publications

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“…One measure of orientation precision is the degree of local misorientation within the scan results [11]. This can be characterized using the kernel average misorientation (KAM) [12,13].…”

Section: Kam Resultsmentioning

confidence: 99%

“…This leads to a diffraction pattern which is essentially a mix of the two diffractions patterns from the two crystal lattices. The mixed pattern can lead to challenges for the indexing algorithm as discussed in detail by Wright et al [11]. As NPAR increases the virtual interaction volume, this could actually lead to a greater fraction of mixed boundaries leading to a lower overall ISR.…”

Section: Grain Boundariesmentioning

confidence: 99%

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Introduction and comparison of new EBSD post-processing methodologies

et al. 2015

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Electron Backscatter Diffraction (EBSD) provides a useful means for characterizing microstructure. However, it can be difficult to obtain index-able diffraction patterns from some samples. This can lead to noisy maps reconstructed from the scan data. Various post-processing methodologies have been developed to improve the scan data generally based on correlating non-indexed or mis-indexed points with the orientations obtained at neighboring points in the scan grid. Two new approaches are introduced (1) a re-scanning approach using local pattern averaging and (2) using the multiple solutions obtained by the triplet indexing method. These methodologies are applied to samples with noise introduced into the patterns artificially and by the operational settings of the EBSD camera. They are also applied to a heavily deformed and a fine-grained sample. In all cases, both techniques provide an improvement in the resulting scan data, the local pattern averaging providing the most improvement of the two. However, the local pattern averaging is most helpful when the noise in the patterns is due to the camera operating conditions as opposed to inherent challenges in the sample itself. A byproduct of this study was insight into the validity of various indexing success rate metrics. A metric based given by the fraction of points with CI values greater than some tolerance value (0.1 in this case) was confirmed to provide an accurate assessment of the indexing success rate.

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“…One measure of orientation precision is the degree of local misorientation within the scan results [11]. This can be characterized using the kernel average misorientation (KAM) [12,13].…”

Section: Kam Resultsmentioning

confidence: 99%

Section: Grain Boundariesmentioning

confidence: 99%

Introduction and comparison of new EBSD post-processing methodologies

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Low quality patterns will also contribute to noise in the cross-correlations, but generally it is assumed for high quality scans that phosphor screen resolution error will be more significant. Wilkinson provides a rough estimate of the error in the distortion calculation due to phosphor screen resolution at around 50 microstrain [4] (Compare this to the worst case 0.5 • accuracy of conventional EBSD [32][33][34][35], which corresponds to almost 9000 microstrain). Mg Cu Ge Fe ∆θ/bL 1/L 2 Figure 4: Calculated GND curves for annealed magnesium, copper, and iron as well as epitaxial germanium at small step sizes.…”

Section: Resultsmentioning

confidence: 99%

“…The individual patterns are then indexed, usually with automated commercial software, recovering the crystal orientation at each point in the scan. Conventional EBSD software indexes individual patterns to find the local lattice orientation to within about 0.1 • via 2D Hough transforms for best case scenarios, with 0.5 • being a conservative estimate [32][33][34][35]. This information may be used to approximate a distortion gradient if strain components of the deformation tensor are neglected [6].…”

Section: Introductionmentioning

confidence: 99%

The effect of length scale on the determination of geometrically necessary dislocations via EBSD continuum dislocation microscopy

Ruggles

Rampton²,

Khosravani

et al. 2016

Ultramicroscopy

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Electron backscatter diffraction (EBSD) dislocation microscopy is an important, emerging field in metals characterization. Currently, calculation of geometrically necessary dislocation (GND) density is problematic because it has been shown to depend on the step size of the EBSD scan used to investigate the sample. This paper models the change in calculated GND density as a function of step size statistically. The model provides selection criteria for EBSD step size as well as an estimate of the total dislocation content. Evaluation of a heterogeneously deformed tantalum specimen is used to asses the method.

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“…A high orientation precision is important for many kinds of misorientation and strain analyses using EBSD .…”

Section: Quantitative Post‐processing Of Bkd Patternsmentioning

confidence: 99%

Electron backscatter diffraction beyond the mainstream

Nolze

Hielscher

Winkelmann

2016

Crystal Research and Technology

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We present special applications of electron backscatter diffraction (EBSD) which aim to overcome some of the limitations of this technique as it is currently applied in the scanning electron microscope. We stress that the raw EBSD signal carries additional information which is useful beyond the conventional orientation determination. The background signal underlying the backscattered Kikuchi diffraction (BKD) patterns reflects the chemical composition and surface topography but also contains channeling-in information which is used for qualitative real-time orientation imaging using various backscattered electron signals. A significantly improved orientation precision can be achieved when dynamically simulated pattern are matched to the experimental BKD patterns. The breaking of Friedel's rule makes it possible to obtain orientation mappings with respect to the point-group symmetries. Finally, we discuss the determination of lattice parameters from individual BKD patterns. Subgrain structure in a single quartz grain. The increased noise level in the left map reflects the lower precision of a standard orientation determination using band detection by the Hough transform. The right map results from the same experimental raw data after orientation refinement using a pattern matching approach. The colors correspond an adapted inverse pole figure color key with a maximum angular deviation of about 2 • from the mean orientation.

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Orientation Precision of Electron Backscatter Diffraction Measurements Near Grain Boundaries

Cited by 44 publications

References 23 publications

Introduction and comparison of new EBSD post-processing methodologies

Introduction and comparison of new EBSD post-processing methodologies

The effect of length scale on the determination of geometrically necessary dislocations via EBSD continuum dislocation microscopy

Electron backscatter diffraction beyond the mainstream

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