Determination of elastic strain fields and geometrically necessary dislocation distributions near nanoindents using electron back scatter diffraction

Wilkinson, Angus J.; Randman, David

doi:10.1080/14786430903304145

Cited by 280 publications

(176 citation statements)

References 32 publications

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“…The methodology and application of the HR-EBSD technique have been well documented [37,[40][41][42][43]46] and recently reviewed by Wilkinson et al [52] and Britton et al [53], hence it is just briefly described here. Forty 128 pixel x 128 pixel regions of interest were randomly placed across each EBSD pattern and comparison of ROIs between test and reference EBSD patterns enables the calculation of displacements corresponding to zone axes shifts.…”

Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

“…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]. Measurement of rotation gradients can be used to evaluate the net curvature and an estimate of GND content [41]. Measurement of residual stress variations within each grain across a map has recently been used to calculate total dislocation measurement [37].…”

Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

“…From this, we calculate the GND densities assuming that 18 types of possible dislocations (12 edges and 6 screws) exist in FCC crystals [55]. This problem is underdetermined so a physically motivated L1 minimisation scheme is used to calculate a set of dislocations with minimum line energy to support measured lattice curvature, ignoring elastic strain gradients as they are typically an order of magnitude smaller than the rotation gradients in metals [41]. This solution may not be unique, but it necessarily supports measured lattice curvatures.…”

Section: Gnd Density Estimationmentioning

confidence: 99%

“…Subsequent analysis to calculate residual stress distributions and stored GND density was performed offline using the HR-EBSD analysis method described elsewhere [40][41][42][43][44]. Briefly, HR-EBSD involves direct pattern comparison of two or more diffraction patterns to determine the lattice rotation and residual elastic strain gradients between the crystals which are illuminated by the electron beam.…”

Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

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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%

Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

Section: Gnd Density Estimationmentioning

confidence: 99%

Section: Ebsd and Hr-ebsd Measurementmentioning

confidence: 99%

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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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“…However, this uncertainty does not affect the GND density as it is only related with lattice curvatures [46].…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

Slip band–grain boundary interactions in commercial-purity titanium

2014

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Dislocation Interactions in Olivine Revealed by HR‐EBSD

et al. 2017

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Interactions between dislocations potentially provide a control on strain rates produced by dislocation motion during creep of rocks at high temperatures. However, it has been difficult to establish the dominant types of interactions and their influence on the rheological properties of creeping rocks due to a lack of suitable observational techniques. We apply high‐angular resolution electron backscatter diffraction to map geometrically necessary dislocation (GND) density, elastic strain, and residual stress in experimentally deformed single crystals of olivine. Short‐range interactions are revealed by cross correlation of GND density maps. Spatial correlations between dislocation types indicate that noncollinear interactions may impede motion of proximal dislocations at temperatures of 1000°C and 1200°C. Long‐range interactions are revealed by autocorrelation of GND density maps. These analyses reveal periodic variations in GND density and sign, with characteristic length scales on the order of 1–10 μm. These structures are spatially associated with variations in elastic strain and residual stress on the order of 10−3 and 100 MPa, respectively. Therefore, short‐range interactions generate local accumulations of dislocations, leading to heterogeneous internal stress fields that influence dislocation motion over longer length scales. The impacts of these short‐ and/or long‐range interactions on dislocation velocities may therefore influence the strain rate of the bulk material and are an important consideration for future models of dislocation‐mediated deformation mechanisms in olivine. Establishing the types and impacts of dislocation interactions that occur across a range of laboratory and natural deformation conditions will help to establish the reliability of extrapolating laboratory‐derived flow laws to real Earth conditions.

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Determination of elastic strain fields and geometrically necessary dislocation distributions near nanoindents using electron back scatter diffraction

Cited by 280 publications

References 32 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

Slip band–grain boundary interactions in commercial-purity titanium

Dislocation Interactions in Olivine Revealed by HR‐EBSD

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