A procedure for indirect and automatic measurement of prior austenite grain size in bainite/martensite microstructures

An alternative procedure for indirect and automatic measurement of the prior austenite grain size (PAGS) in bainite/martensite is proposed in this work. It consists in the determination of an effective grain size (EGS) by means of statistical post-processing of electron backscatter diffraction (EBSD) data. The algorithm developed for that purpose, which is available on-line, has been applied to simulated EBSD maps as well as to both a nanocrystalline bainitic steel and a commercial hot-rolled air-cooled steel with a granular bainitic microstructure. The new proposed method has been proven to be robust and results are in good agreement with conventional PAGS measurements. The added value of the procedure comes from its simplicity, as no parent reconstruction is involved during the process, and its suitability for low-magnification EBSD maps, thus allowing a large step-size and coverage of a substantially broader area of the sample than the previous methods reported.
Spanish Ministry of Economy and Competitiveness for funding this research under the contract IPT-2012-0320-420000. L.M.-R. also acknowledges the Spanish Ministry of Economy and Competitiveness for financial support in the form of a PhD research grant (FPI-Ref. BES-2011-044186).