After Friction Stir Processing of this aluminium alloy, KAM and Grain Boundary maps are obtained by EBSD. It shows, the region of blue colored recrystallized grains in KAM map correspond to the region of grains having substructures (prominence of low-angle grain boundaries) in Grain Boundary map. However, the continuous dynamic recrystallization by a severe plastic deformation process should form recrystallized grains surrounded by high angle grain boundaries without any substructures. This recrystallization also could be predicted from KAM maps. What is the explanation for this apparent discrepancy between obtained grain boundary maps and KAM maps?
Not necessarily the correct answer, but do not forget that your EBSD software typically has a discrete threshold to define a high-angle grain boundary, and an angular and spatial resolution that will influence the detection of low-angle boundaries. Depending upon the selected threshold value (if I recall correctly it is often set at an initial value of 15°) and the angular and spatial resolution, you might get very different maps. Although angular and spatial resolution are often not that easy to 'play' with (as they are often defined by the limits of your EBSD system, material preparation technique and desired scan size), changing the high-angle boundary threshold is often relatively straightforward. One of the things I used to do in the past, was to play with the threshold until the average optical and EBSD grain size corresponded (but generally after filtering and cleaning up of the EBSD data, so you need to know what your doing, and I am of course assuming it is possible to get an average grain size using optical microscopy which may not be possible for friction stir processed materials).
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Metals
- Alloys