Mapping of lattice distortion in martensitic steel-Comparison of different evaluation methods of EBSD patterns

Grzegorz Cios; Aimo Winkelmann; Gert Nolze; Tomasz Tokarski; Łukasz Rychłowski; Leonid Dan; Piotr Bała

doi:10.1016/j.ultramic.2023.113824

Mapping of lattice distortion in martensitic steel-Comparison of different evaluation methods of EBSD patterns

Ultramicroscopy. 2023 Nov:253:113824. doi: 10.1016/j.ultramic.2023.113824. Epub 2023 Aug 3.

Authors

Grzegorz Cios¹, Aimo Winkelmann², Gert Nolze³, Tomasz Tokarski², Łukasz Rychłowski², Leonid Dan², Piotr Bała⁴

Affiliations

¹ Academic Centre for Materials and Nanotechnology, AGH University of Krakow, al. A. Mickiewicza 30, 30-059 Kraków, Poland. Electronic address: Ciosu@agh.edu.pl.
² Academic Centre for Materials and Nanotechnology, AGH University of Krakow, al. A. Mickiewicza 30, 30-059 Kraków, Poland.
³ Federal Institute for Materials, Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany; TU Bergakademie Freiberg, Institute for Mineralogy, Brennhausgasse 14, 09596 Freiberg, Germany.
⁴ Academic Centre for Materials and Nanotechnology, AGH University of Krakow, al. A. Mickiewicza 30, 30-059 Kraków, Poland; Faculty of Metals and Industrial Computer Science, AGH University of Krakow, al. A. Mickiewicza 30, 30-059 Kraków, Poland.

PMID: 37572392
DOI: 10.1016/j.ultramic.2023.113824

Abstract

To visualize the varying tetragonal distortions in high carbon martensitic steels by EBSD, two different approaches have been applied on backscattered Kikuchi diffraction (BKD) patterns. A band-edge refinement technique called Refined Accuracy (RA) (Oxford Instruments) is compared with a technique called Pattern Matching (PM), which optimizes the fit to a simulated BKD signal. RA distinguishes between hypothetical phases of different fixed c/a, while PM determines a best fitting continuous c/a by projective transformation of a master pattern. Both techniques require stored BKD patterns. The sensitivity of the c/a-determination was tested by investigating the microstructure of a ferritic steel with an expected c/a=1. The influence of the Kikuchi pattern noise on c/a was compared for a single or 40 averaged frames per measuring point, and turned out to be not significant. The application of RA and PM on the martensitic microstructure delivered qualitatively similar maps of c/a. The comparison of RA and PM shows that RA is suitably fast and precise during mapping the martensite c/a ratio in analyses of high carbon martensite, especially for fast initial surveys. As RA leads quantitatively to higher noise in c/a, the PM analysis can be used for higher precision results.

Keywords: EBSD; Martensite; Steel; Strain; Tetragonality.