Calibration of Crystal Orientation and Pattern Center of EBSD using Integrated Digital Image Correlation
Résumé
The accuracy of electron backscatter diffraction indexation has long been limited by pattern center determination, and numerous hardware and software methods have been proposed to improve the calibration. Here, an Integrated Digital Image Correlation (IDIC) procedure is proposed to determine simultaneously crystal orientation and pattern center by registering experimental and simulated electron diffraction patterns. To assess the performance and robustness of the procedure, numerous case studies are reported. Noise sensitivity is first explored on virtual data to assess convergence conditions and result uncertainty up to high noise level and small detector size. Two experimental data sets are further exploited. First, a high-definition detector shows that crystal orientation uncertainty as low as 3×10 −2 degrees can be achieved, that is at least 80% less than commercial Hough-transformation based indexation method. Different sample tilt angles are tested, IDIC indexation proves much more tolerant with imprecise tilt angles than common EBSD indexation methods. Second, fast EBSD acquisitions with a coarse definition performed during an in-situ tensile test are analyzed. A quantification of the residual noise allows one to formulate an optimized IDIC functional with a proper pixel-wise weight. With the latter refinement a two-pass procedure leads to a much enhanced precision of the determination of crystal orientation, giving access to more precise evaluation of maps of geometrically necessary dislocation densities.
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