Factors affecting the accuracy of high resolution electron backscatter diffraction when using simulated patterns

Britton, T. Ben; Maurice, Claire; Fortunier, Roland; Driver, J.H.; Day, A. P.; Meaden, Graham; Dingley, David J.; Mingard, Ken

doi:10.1016/j.ultramic.2010.08.001

Cited by 125 publications

(111 citation statements)

References 33 publications

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“…1 μm for this experimental set up). [45]. The direct pattern comparison to extract elastic strain and lattice rotation was developed initially by Wilkinson et al [40,46] and markedly improved and optimised in the past few years especially using robust fitting [42], pattern remapping routines to calculate strains in the presence of larger lattice rotations [43].…”

Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

On the mechanistic basis of fatigue crack nucleation in Ni superalloy containing inclusions using high resolution electron backscatter diffraction

et al. 2015

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This is an authors' copy of a manuscript published in Acta Materialia Volume 97, 15 September 2015, Pages 367-379. http://dx.doi.org/10.1016/j.actamat.2015.06.035 AbstractA series of interrupted three-point bend low-cycle fatigue tests were carried out on a powder metallurgy FHG96 nickel superalloy sample containing non-metallic inclusions. High resolution electron backscatter diffraction (HR-EBSD) was used to characterize the distribution and evolution of geometrically necessary dislocation (GND) density, residual stress and total dislocation density near a non-metallic inclusion. A systematic study of room temperature cyclic deformation is presented in which slip localisation, cyclic hardening, ratcheting and stabilisation occur, through to crack formation and microstructurally-sensitive propagation. Particular focus is brought to bear at the inclusion-matrix interface. Complex inhomogeneous deformation structures were directly observed from the first few loading cycles, and these structures were found not to vary significantly with increasing number of cycles. A clear link was observed between crack nucleation site and microstructurally-sensitive growth path and the spatially-resolved sites of extreme values of residual stress and GND density.

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Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

On the mechanistic basis of fatigue crack nucleation in Ni superalloy containing inclusions using high resolution electron backscatter diffraction

et al. 2015

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“…The value of 2.0 lm can be put into perspective by comparison to previous studies of precision in the EBSD method. 4,5,8,[12][13][14] In these investigations, minimum error values near 0.2%-0.5% of the pattern width (%100 lm) are quoted for the precision of the current standard methods of projection center determination. The error estimated for the setup used here indicates an improvement by at least one order of magnitude and is approaching values claimed for high-precision shadow-grid methods (0.5 lm 14 ) and for the moving screen technique combined with image correlation (theoretically <1 lm, but larger in practice due to optical and mechanical effects 13 ).…”

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confidence: 95%

“…2 As an accurate knowledge of the projection center is necessary to calibrate the angular coordinates of the Kikuchi pattern on the detector screen, a key problem in EBSD is the determination of the exact position of the electron beam spot relative to the detector. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] We have previously used a digital hybrid pixel detector, Timepix, 20,21 in a SEM to obtain Kikuchi patterns from crystalline samples 22 by direct electron detection. Detailed investigations revealed that the Timepix detector response exhibits an underlying diffraction pattern even in the total absence of diffraction effects from the sample (see Fig.…”

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Diffractive triangulation of radiative point sources

Vespucci

Naresh-Kumar

Trager-Cowan

et al. 2017

Applied Physics Letters

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We describe a general method to determine the location of a point source of waves relative to a two-dimensional single-crystalline active pixel detector. Based on the inherent structural sensitivity of crystalline sensor materials, characteristic detector diffraction patterns can be used to triangulate the location of a wave emitter. The principle described here can be applied to various types of waves provided that the detector elements are suitably structured. As a prototypical practical application of the general detection principle, a digital hybrid pixel detector is used to localize a source of electrons for Kikuchi diffraction pattern measurements in the scanning electron microscope. This approach provides a promising alternative method to calibrate Kikuchi patterns for accurate measurements of microstructural crystal orientations, strains, and phase distributions

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“…The use of simulations to generate the reference patterns is an obvious approach to solving the 'reference pattern problem' and has been explored by several groups [8,9]. The simulations must have sufficient fidelity and while crude kinematic methods are unacceptable, dynamical simulation show promise [8,9,10]. Aberrations in the EBSD detector optics can lead to significant artifacts in the measured strains [9] and so need to be determined and accounted for using methods given for example by Day [11].…”

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confidence: 99%

“…The simulations must have sufficient fidelity and while crude kinematic methods are unacceptable, dynamical simulation show promise [8,9,10]. Aberrations in the EBSD detector optics can lead to significant artifacts in the measured strains [9] and so need to be determined and accounted for using methods given for example by Day [11]. However, the remaining barrier to successfully using simulations is the limited accuracy of currently available methods for determining the camera geometry.…”

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confidence: 99%

High Accuracy EBSD - A Review of Recent Applications, Innovations, and Remaining Challenges

Wilkinson

Jiang

Meaden³

et al. 2011

Microsc Microanal

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The implementation of cross-correlation analysis of EBSD patterns has allowed much improved angular sensitivity measurements to be achieved including the ability to determine the variations in elastic strains [1,2]. Cross-correlation functions between tests patterns and a reference pattern are calculated at selected sub-regions distributed across the patterns. A simple geometric analysis then allows the elastic strains and lattice rotations to be calculated from the shifts measured at these subregions. Sub-pixel resolution on the pattern shifts, typically to ±0.05 or better, leads to strain and rotation sensitivity of~±10 -4 . In many situations a convenient location on the sample can be used to generate a reference pattern for which the strain state is well known, and in most cases zero. This is the case when studying the flow fields and residual stresses near indents in single crystals. . Analysis of deformation fields near crack tips and particles are important situations where strains fall to negligible levels in the far field so that good reference patterns can be obtained from regions well away from the crack or particle [2,6,7]. In many more situations, such as a plastically deformed polycrystal, there is no obvious position on the sample from which to obtain a reference pattern corresponding to a known strain state. Fixing the absolute level of the strains in these situations remains the most significant challenge in continuing the development of the technique. One approach is to combine the local strain variations measured using the EBSD method with modeling at a longer length scale. A uniform strain state is then added to the measured EBSD strain variations to bring the average values into agreement with the model [6]. If characterizing the resulting deformation sub-structure is the main aim of the work then Nye's dislocation tensor analysis can be used to estimate the geometrically necessary dislocation (GND) density. This requires only gradients in the elastic strain and lattice rotation fields and so avoids the problem of assigning the absolute strain values. In all metal deformation studies we have made plastic flow results in rotations that are markedly larger than the elastic strains which can then be ignored when estimating the GND content. Indeed the lattice rotations can be sufficiently large so as to cause the cross-correlation analysis to give incorrect pattern shifts for parts of the pattern which change too much. We have recently implemented a robust fitting algorithm which identifies regions of the pattern for which the pattern shifts are suspect and down-weights their influence in an iterative scheme to determine the strain and rotation from the pattern shifts. This allows fuller coverage of the EBSD map as illustrated in FIG 2 (b) and (c) for a Cu sample deformed to 10% in tension. The use of simulations to generate the reference patterns is an obvious approach to solving the 'reference pattern problem' and has been explored by several groups [8,9]. The simulations must have sufficient ...

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Factors affecting the accuracy of high resolution electron backscatter diffraction when using simulated patterns

Cited by 125 publications

References 33 publications

On the mechanistic basis of fatigue crack nucleation in Ni superalloy containing inclusions using high resolution electron backscatter diffraction

On the mechanistic basis of fatigue crack nucleation in Ni superalloy containing inclusions using high resolution electron backscatter diffraction

Diffractive triangulation of radiative point sources

High Accuracy EBSD - A Review of Recent Applications, Innovations, and Remaining Challenges

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