Automated high-resolution backscattered-electron imaging at macroscopic scale

TL;DR

This paper introduces a novel method for generating high-resolution SEM images across multiple scales, enabling detailed microscopic analysis over large physical areas, exemplified on a high entropy alloy.

Contribution

It combines SEM imaging, video stitching, denoising, and segmentation to produce macroscopic images with submicron details, expanding SEM capabilities at the macro scale.

Findings

Hardness correlates positively with BCC phase content.

Hardness negatively correlates with lamella width.

Segmentation enables microstructure analysis over large areas.

Abstract

Scanning electron microscopy (SEM) has been widely utilized in the field of materials science due to its significant advantages, such as large depth of field, wide field of view, and excellent stereoscopic imaging. However, at high magnification, the limited imaging range in SEM cannot cover all the possible inhomogeneous microstructures. In this research, we propose a novel approach for generating high-resolution SEM images across multiple scales, enabling a single image to capture physical dimensions at the centimeter level while preserving submicron-level details. We adopted the SEM imaging on the AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) as an example. SEM videos and image stitching are combined to fulfill this goal, and the video-extracted low-definition (LD) images are clarified by a well-trained denoising model. Furthermore, we segment the macroscopic image of the EHEA, and area of various microstructures are distinguished. Combining the segmentation results and hardness experiments, we found that the hardness is positively correlated with the content of body-centered cubic (BCC) phase, negatively correlated with the lamella width, and the relationship with the proportion of lamellar structures was not significant. Our work provides a feasible solution to generate macroscopic images based on SEMs for further analysis of the correlations between the microstructures and spatial distribution, and can be widely applied to other types of microscope.