Automated classification of granular bainite and polygonal ferrite by electron backscatter diffraction verified through local structural and mechanical analyses

• Published in: Journal of materials research Vol. 38; no. 18; pp. 4177 - 4191
• Main Authors: Jentner, R. M., Tsai, S. P., Welle, A., Scholl, S., Srivastava, K., Best, J. P., Kirchlechner, C., Dehm, G.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 28-09-2023; Springer Nature B.V
• Subjects: Applied and Technical Physics; Bainite; Biomaterials; Chemical properties; Chemistry and Materials Science; Classification; Electron backscatter diffraction; Grain structure; High strength low alloy steels; Inorganic Chemistry; Iron constituents; Materials Engineering; Materials research; Materials Science; Misalignment; Nanohardness; Nanoindentation; Nanotechnology; Polygons
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/s43578-023-01113-7

Differentiation of granular bainite and polygonal ferrite in high-strength low-alloy (HSLA) steels possesses a significant challenge, where both nanoindentation and chemical analyses do not achieve an adequate phase classification due to the similar mechanical and chemical properties of both constituents. Here, the kernel average misorientation from electron backscatter diffraction (EBSD) was implemented into a Matlab code to differentiate and quantify the microstructural constituents. Correlative electron channeling contrast imaging (ECCI) validated the automated phase classification results and was further employed to investigate the effect of the grain tolerance angle on classification. Moreover, ECCI investigations highlighted that the grain structure of HSLA steels can be subdivided into four grain categories. Each category contained a different nanohardness or substructure size that precluded a nanoindentation-based phase classification. Consequently, the automated EBSD classification approach based on local misorientation achieved a reliable result using a grain tolerance angle of 5°.
Graphical abstract