Influence of Noise-Generating Factors on Cross-Correlation Electron Backscatter Diffraction (EBSD) Measurement of Geometrically Necessary Dislocations (GNDs)

• Published in: Microscopy and microanalysis Vol. 23; no. 3; pp. 460 - 471
• Main Authors: Hansen, Landon T., Jackson, Brian E., Fullwood, David T., Wright, Stuart I., De Graef, Marc, Homer, Eric R., Wagoner, Robert H.
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.06.2017; Oxford University Press; Microscopy Society of America (MSA)
• Subjects: Accuracy; Alignment; Blocking; Bulk density; Channel pores; Compression; Computation; Computer applications; Computer memory; Cost analysis; Crystal structure; Data transfer (computers); Diffraction; Dislocation; Distortion; Draper protein; Edge dislocations; Electron backscatter diffraction; Error analysis; Formulas (mathematics); Fourier analysis; Fourier transforms; Grain boundaries; High resolution; Image processing; Lanthanum; Mapping; Materials Science; Materials Science Applications; Mechanical engineering; Microscopy; Noise; Periodicity; Projection; Quality; Scattering; Segmentation; Sensitivity; Sensors; Subtraction; Tungsten; noise; simulated electron backscatter diffraction; HR-EBSD; binning; cross-correlation; compression
• ISSN: 1431-9276; 1435-8115
• DOI: 10.1017/S1431927617000204

Studies of dislocation density evolution are fundamental to improved understanding in various areas of deformation mechanics. Recent advances in cross-correlation techniques, applied to electron backscatter diffraction (EBSD) data have particularly shed light on geometrically necessary dislocation (GND) behavior. However, the framework is relatively computationally expensive—patterns are typically saved from the EBSD scan and analyzed offline. A better understanding of the impact of EBSD pattern degradation, such as binning, compression, and various forms of noise, is vital to enable optimization of rapid and low-cost GND analysis. This paper tackles the problem by setting up a set of simulated patterns that mimic real patterns corresponding to a known GND field. The patterns are subsequently degraded in terms of resolution and noise, and the GND densities calculated from the degraded patterns using cross-correlation ESBD are compared with the known values. Some confirmation of validity of the computational degradation of patterns by considering real pattern degradation is also undertaken. The results demonstrate that the EBSD technique is not particularly sensitive to lower levels of binning and image compression, but the precision is sensitive to Poisson-type noise. Some insight is also gained concerning effects of mixed patterns at a grain boundary on measured GND content.