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

Ruggles, Timothy; Rampton, Travis; Khosravani, Ali; Fullwood, David T.

doi:10.1016/j.ultramic.2016.03.003

Cited by 54 publications

(18 citation statements)

References 44 publications

(70 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This simple approach contrasts with those employed in previous work on metals where the multitude of slip systems requires additional assumptions or constraints to select one of many possible combinations of dislocation types and densities to fit the measured lattice orientation gradients (Jiang et al, ; Wilkinson & Randman, ). The apparent density of GNDs depends on the mapping step size and, to a lesser extent, on the binning of pixels in diffraction patterns (Jiang et al, ; Ruggles et al, ; Wallis et al, ). Wallis et al () presented a detailed assessment of these effects for the same map of PI‐1433 as used in this study.…”

Section: Methodsmentioning

confidence: 99%

Dislocation Interactions in Olivine Revealed by HR‐EBSD

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

Section: Methodsmentioning

confidence: 99%

Dislocation Interactions in Olivine Revealed by HR‐EBSD

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Then dislocation analysis from EBSD data is discussed. The main drawbacks of using EBSD data for quantitative analysis are related to the influence of the measurement noise and of the EBSD mapping step size [14][15][16][17][18][19][20]. A method based on the one originally proposed by Kamaya [21], described in the section 3.1, is applied to reduce those drawbacks.…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis of dislocations and dislocation boundaries from EBSD data

et al. 2017

View full text Add to dashboard Cite

Electron BackScatter Diffraction (EBSD) is often used for semi-quantitative analysis of dislocations in metals. In general, disorientation is used to assess Geometrically Necessary Dislocations (GNDs) densities. In the present paper, we demonstrate that the use of disorientation can lead to inaccurate results. For example, using the disorientation leads to different GND density in recrystallized grains which cannot be physically justified. The use of disorientation gradients allows accounting for measurement noise and leads to more accurate results. Misorientation gradient is then used to analyze dislocations boundaries following the same principle applied on TEM data before. In previous papers, dislocations boundaries were defined as Geometrically Necessary Boundaries (GNBs) and Incidental Dislocation Boundaries (IDBs). It has been demonstrated in the past, through transmission electron microscopy data, that the probability density distribution of the disorientation of IDBs and GNBs can be described with a linear combination of two Rayleigh functions. Such function can also describe the probability density of disorientation gradient obtained through EBSD data as reported in this paper. This opens the route for determining IDBs and GNBs probability density distribution functions separately from EBSD data, with an increased statistical relevance as compared to TEM data. The method is applied on deformed Tantalum where grains exhibit dislocation boundaries, as observed using electron channeling contrast imaging.

show abstract

“…Moreover, EBSD analysis can be performed with step sizes as low as 20 nm (e.g. Ruggles et al ., ), allowing for the analysis of ultrafine material. Although the quality of FA pole figures is exceptionally lower than EBSD and ND techniques (Figs.…”

Section: Discussionmentioning

confidence: 99%

Comparison of quartz crystallographic preferred orientations identified with optical fabric analysis, electron backscatter and neutron diffraction techniques

Hunter

Wilson

Luzin

2016

Journal of Microscopy

View full text Add to dashboard Cite

Three techniques are used to measure crystallographic preferred orientations (CPO) in a naturally deformed quartz mylonite: transmitted light cross-polarized microscopy using an automated fabric analyser, electron backscatter diffraction (EBSD) and neutron diffraction. Pole figure densities attributable to crystal-plastic deformation are variably recognizable across the techniques, particularly between fabric analyser and diffraction instruments. Although fabric analyser techniques offer rapid acquisition with minimal sample preparation, difficulties may exist when gathering orientation data parallel with the incident beam. Overall, we have found that EBSD and fabric analyser techniques are best suited for studying CPO distributions at the grain scale, where individual orientations can be linked to their source grain or nearest neighbours. Neutron diffraction serves as the best qualitative and quantitative means of estimating the bulk CPO, due to its three-dimensional data acquisition, greater sample area coverage, and larger sample size. However, a number of sampling methods can be applied to FA and EBSD data to make similar approximations.

show abstract

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

Cited by 54 publications

References 44 publications

Dislocation Interactions in Olivine Revealed by HR‐EBSD

Dislocation Interactions in Olivine Revealed by HR‐EBSD

Statistical analysis of dislocations and dislocation boundaries from EBSD data

Comparison of quartz crystallographic preferred orientations identified with optical fabric analysis, electron backscatter and neutron diffraction techniques

Contact Info

Product

Resources

About