Abstract
A discrete two-dimensional Fourier transform and the power Fourier spectrum are used for determination of average strains near cracks in a welded seam of Ni-Cr-Fe alloy. The alignment of Kikuchi images with the help of genetic algorithms and subtraction of white Gaussian noise made it possible to more fully take into account the influence of instrumental factors on the formation of electron backscatter diffraction patterns.
Highlights
Structural violations of the lattice near cracks in a welded seam of Ni-Cr-Fe alloy appear in the characteristic changes of spatial distribution of brightness of electron diffraction images (Kikuchi patterns), in particular: the change of the distance between axes of zones [1,2,3] and angles between Kikuchi bands [4], as well as the change in the width [3, 5] and integral intensity [3, 6] of the Kikuchi band profiles
The analysis of the energy spectrum of Kikuchi band images, which is calculated on the basis of a two-dimensional Fourier transform, is proposed for determination of local deformations of crystals
The energy spectrum is calculated for the whole image, which reduces the effect of distortions of experimental Kikuchi images on the accuracy of determining the local deformations of crystals
Summary
Structural violations of the lattice near cracks in a welded seam of Ni-Cr-Fe alloy appear in the characteristic changes of spatial distribution of brightness of electron diffraction images (Kikuchi patterns), in particular: the change of the distance between axes of zones [1,2,3] and angles between Kikuchi bands [4], as well as the change in the width [3, 5] and integral intensity [3, 6] of the Kikuchi band profiles. The experimental images of Kikuchi bands are more or less blurred, which greatly limits the accuracy of band profiles reading. The analysis of the energy spectrum of Kikuchi band images, which is calculated on the basis of a two-dimensional Fourier transform, is proposed for determination of local deformations of crystals. The energy spectrum is calculated for the whole image, which reduces the effect of distortions of experimental Kikuchi images on the accuracy of determining the local deformations of crystals. The expressiveness of this approach and its integral nature substantially complement existing methods for determining deformations from Kikuchi's images
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