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Results for “CC-EBSD”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Comparison of dislocation characterization by electron channeling contrast imaging and cross-correlation electron backscattered diffraction

In this paper, the relative capabilities and limitations of electron channeling contrast imaging (ECCI) and cross-correlation electron backscattered diffraction (CC-EBSD) have been assessed by studying the dislocation distributions resulting from nanoindentation in body centered cubic Ta. Qualitative comparison reveals very similar dislocation distributions between the CC-EBSD mapped GNDs and the ECC imaged dislocations. Approximate dislocation densities determined from ECC images compare well to those determined by CC-EBSD. Nevertheless, close examination reveals subtle differences in the details of the distributions mapped by these two approaches. Finally, the details of the dislocation Burgers vectors and line directions determined by ECCI have been compared to those determined using CC-EBSD and reveal good agreement.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Comparison of Dislocation Characterization by Electron Channeling Contrast Imaging and Cross-Correlation Electron Backscattered Diffraction

The characterization and quantification of dislocations is predominately carried out using transmission electron microscopy (TEM). Nevertheless, the sample preparation necessary for TEM foils can be cumbersome and possibly introduce defects. Two other techniques for characterizing and quantifying dislocations are electron channeling contrast imaging (ECCI) and cross-correlation electron backscattered diffraction (CC-EBSD). ECCI is similar to TEM in that specific imaging (channeling or diffraction) conditions need to be established, but is carried out in a scanning electron microscope on bulk samples, resulting in less complex sample preparation. CC-EBSD measures subtle changes in orientation measured from EBSD patterns to calculate elastic strains and the Nye tensor to deduce and map the total geometrically necessary dislocation (GND) content. Furthermore, this work presented here compares the capabilities of ECCI and CC-EBSD to map dislocations generated from nanoindentation.

42 ENGINEERING↗
DOE OSTI2018

Resolving pseudosymmetry in γ-TiAl using cross-correlation electron backscatter diffraction with dynamically simulated reference patterns

Pseudosymmetry is a phenomenon that occurs when grains with different lattice parameters produce nearly identical diffraction patterns such that conventional electron backscatter diffraction (EBSD) techniques are unable to unambiguously differentiate the lattice orientations. This commonly occurs in materials with near-unity tetragonality, such as γ-TiAl. The current study uses cross-correlation EBSD to resolve pseudosymmetry in γ-TiAl. Three dynamically simulated reference patterns are generated for each point in the scan, one for each of the three potential pseudosymmetric orientations, which are subsequently correlated with the original pattern using six different methods in order to identify the correct orientation. The methods are first applied to a scan of dynamically simulated patterns, which is used to evaluate the sensitivity of the method to pattern resolution, pattern noise and pattern center error. It was determined that all six methods were 100% successful up to about 13 µm of pattern center error and pattern resolutions of about 80 × 80 pixels, and hence the methods were applied to an experimental sample of lamellar γ-TiAl. A hybrid combination of two of the methods was shown to successfully select the correct pseudosymmetry for about 96% of the points in the scan, improving upon the 70% accuracy of the Hough-based methods for the current study and 90% accuracy for previous studies resolving pseudosymmetry in lamellar γ-TiAl.

36 MATERIALS SCIENCE↗