A Step Size Dependence of Kam, Grod and Gnd Parameters Calculated from Ebsd

Abstract

In the past decade, EBSD detectors underwent a dramatic improvement in their angular resolution and acquisition speed. The angular resolution at the level of 0.05° enables measurements of crystal misorientations which are traditionally measured via TEM techniques. Automatic acquisition of large amount of quantitative data suitable for statistical analysis is the crucial advantage of the EBSD over TEM and STEM techniques. Post-processing methods like Kernel Average Misorientation (KAM), Grain reference Orientation Deviation (GROD) and Geometrically Necessary Dislocations (GND) correlate with the dislocation density. Therefore, these parameters can provide information about the deformation state of the microstructure and serve as an input for research purposes or as an engineering parameter. However, these parameters are highly sensitive to the step size (spatial resolution) of the EBSD map. This study describes the influence of the step size on the advanced EBSD parameters with experimentally acquired EBSD maps of cyclically deformed 316 steel. The correlation between the deformation intensity (strain amplitude) and the EBSD parameters further demonstrates the importance of step size, and the usefulness of the advanced EBSD methodology. Although the step size is the focus of the study, the angular resolution of the EBSD is also discussed. Finaly, the results obtained by the EBSD are correlated with the STEM micrographs to critically assess both strengths and weaknesses of the modern EBSD analysis.

Keywords: EBSD, resolution, plastic deformation, fatigue