Normally only two pronounced maxima (at 5to20 and 50to60 degs) are observed. I wonder whether the mentioned feature at about 30dg may be due to 1. Poor local diffraction (say in terms of CI), 2. Considering only CLOSED boundaries rather than any segments,3. Some computation details ("black box" effect) by standard EBSD softwares?.
Could you post the graphs you are explaining? I think I know what do you mean, but it is better to see it. 30 degrees always looks like a pseudosymmetry problem caused by weak patterns and ghost peaks. Increase CI and look whether these peaks disappear. Then you know at least that it is related to unreliably indexed patterns, which does not mean bad patterns. It only tells you that there are two solutions which are very similar (bad). If this is not the case...30° is an angle between two-fold rotation axis. Is it really excluded that you have a hexagonal modification as additional phase? I would give it a try. Sometimes very strange things happens (epsilon martensite).
Thanks, Gert!
I think your answer is relevant. As to an example, I can send it after this weekend.
Attached is an example where on an IQ map artifact small 'bubbles' with virtually high-angle boundaries are superimposed. Evidently the bad diffraction areas give the 30dg peak. Besides, I have heard that similar peaks were observed even on single crystals with poorly prepared sections. Ubfortunately I have no exact reference to such an interesting event.
This looks like an artifact caused by a improper phase setup. Could you increase slightly the number of reflectors used during indexing, and the number of bands detected? What are you using currently? I have to admit that I am not very familiar with the EDAX system, but I am quite sure that they have settings to prevent these misindexings at least in the "nice" grains. Whether this will work in the same way for the bainite-martensite areas we will see. But I am also not very pessimistic. Otherwise, I need the sample since I usually save all patterns (Bruker) and can the look at each position and can reprocess the patterns again. You might be able to do this as well, but it is more "unpopular feature". For me it is perfect since I have total control and no black box. :-)
We use SEM Quanta 200 3D with Edax TSL soft. I afraid it is hardly possible to get into settings.. Anyway, the trial increase of CI threshold reduces the considered peak while approx. keeping the spectrum in other respects. This is enough reason in my opinion just to smooth it out numerically (with initial data). Thanks a lot for your interest however this little (soluble) trouble will not cost FURTHER special efforts.
I have no experience with Bruker but you could do almost everything with TSL-OIM package. settings Gert mentioned are accessible through the Hough setting window ...
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