Effective elimination of Moiré fringe at the nanoprecipitate/matrix interface

TL;DR

This paper introduces a method to eliminate Moiré fringes in images of nanoprecipitates in steel, revealing clearer crystal structures and strain distributions.

Contribution

A novel method for removing Moiré fringes using FFT and IFFT to improve strain measurement accuracy in nanoprecipitates.

Findings

The method successfully reveals hidden lattice fringes of MC carbide in the austenite matrix.

Artifact-free strain distribution was observed in MC carbide-containing areas using the proposed technique.

The process was effective in analyzing inclined twin interfaces in BCC steel with overlapping lattice fringes.

Abstract

The effective method for eliminating the Moiré fringes in the MC nanoprecipitates in the austenite matrix was studied. Considering the dynamic diffraction between the matrix and precipitate, the spots originating from the Moiré pattern were selected in the fast Fourier transform (FFT) pattern. The Moiré fringe image was extracted by performing inverse FFT(IFFT) of the selected spots. Subtracting the Moiré fringe contribution from the original image intensity reveals the veiled lattice fringes of MC carbide in the austenite matrix. The image was compared and discussed with the IFFT image of the direct selection of the matrix + MC FFT patterns. The suggested method was applied to strain measurement in the MC carbide-containing area using the geometrical phase analysis. Compared with the result obtained from the raw image containing Moiré fringes, the applied method shows artifact-free strain distribution in the MC carbide. The process was applied to the inclined twin interface in BCC steel. The lattice fringe in the overlapping area shows a more detailed lattice feature. This novel study sheds light on the veiled crystal structure and strain distribution under various conditions where more than two lattice fringes overlap.

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