Automated Grain Boundary Detection for Bright-Field Transmission Electron Microscopy Images via U-Net

DOI

10.1093/micmic/ozad115

Document Type

Journal Article

Publication Date

12-1-2023

Publication Title

Microscopy and Microanalysis

Volume

29

Issue

6

First Page

1968

Last Page

1979

ISSN

14319276

Keywords

automated grain boundary detection, bright-field transmission electron microscopy, grain size distribution, machine learning, nanocrystalline thin films

Abstract

Quantification of microstructures is crucial for understanding processing-structure and structure-property relationships in polycrystalline materials. Delineating grain boundaries in bright-field transmission electron micrographs, however, is challenging due to complex diffraction contrast in images. Conventional edge detection algorithms are inadequate; instead, manual tracing is usually required. This study demonstrates the first successful machine learning approach for grain boundary detection in bright-field transmission electron micrographs. The proposed methodology uses a U-Net convolutional neural network trained on carefully constructed data from bright-field images and hand tracings available from prior studies, combined with targeted postprocessing algorithms to preserve fine features of interest. The image processing pipeline accurately estimates grain boundary positions, avoiding segmentation in regions with intragrain contrast and identifying low-contrast boundaries. Our approach is validated by directly comparing microstructural markers (i.e., grain centroids) identified in U-Net predictions with those identified in hand tracings; furthermore, the grain size distributions obtained from the two techniques show notable overlap when compared using t-test, Kolmogorov-Smirnov test, and Cramér-von Mises test. The technique is then successfully applied to interpret new microstructures having different image characteristics from the training data, with preliminary results from platinum and palladium microstructures presented, highlighting the versatility of our approach for grain boundary identification in bright-field micrographs.

Open Access

Hybrid_Gold

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