Improving parent-austenite twinned grain reconstruction using electron backscatter diffraction in low carbon austenite

Abstract

Thermomechanical controlled processing (TMCP) is widely used to optimize the final properties of high strength low alloy (HSLA) steels, via microstructure engineering. The room temperature microstructures are influenced by the high temperature austenite phase, and the austenite microstructure can be accessed by reconstruction using electron backscatter diffraction (EBSD) data of the final microstructure. A challenge for reconstruction of the parent austenite grain (PAG) microstructure and subsequent austenite grain size measurement is the presence of austenite-phase annealing twins, and we address this challenge with a new ‘re-sort’ algorithm. Our algorithm has been validated using the retained austenite regions (which were recovered via advanced pattern matching of EBSD patterns). We demonstrate that the re-sort algorithm improves the PAG reconstruction significantly, especially for the grain boundary network and correlation with other methods of grain size assessment and development of TMCP steels.