For high-resolving (angular) interpretations of EBSD patterns, e.g. for GND analysis or the characterisation of the microstructure of pseudo-symmetric phases (photovoltaic phases like I-III-VI semiconductors (chalcopyrites), domain-rich phases like perovskites etc), tiny deviations in band detection can be essential for the determination of small or even huge misorientations (differenciation between a and c axes). I wonder whether anybody seriously discussed this phenomenon as critical error source, e.g. related to the Hough resolution or pattern resolution used for the Hough transform?
You mean the zone axes? This is quite surprizing since as far as I know this was one reason to introduce the Hough transform and go away from the originally used zone axes for orientation determination by EBSD. For TEM it seems to be different since the Kossel lines are much sharper than Band edges and deviations from straight lines are even smaller. I guess finally it doesn't change that much whether one uses lattice or reciprocal lattice directions since (hkl)_1 x (hkl)_2 = [uvw] and vice versa. It is more a question what can be better experimentally extracted. Nevertheless, thanks for the reference. Maybe, I am overlooking something...
Hi Xinfu, the challange is to detect bcc and bct, i.e. ferrite and martensite. The discrimination between fcc and bcc is standard for any EBSD system. (but maybe you mistyped it?)
What happens when you select fcc and bcc instead of fcc and bct? Does it also index reliably? I havn't heard about 8% tetragonal distortion in martensite (in steel, or about which kind of martensite you are talking)?
Tetragonality is reported to be already detectable at 5%. Some papers claim that they even could detect 2% which I personally don't believe. Here I guess that a systematic misinterpretation of band centers causes a virtual systematic indexing which is interpreted as correct since it does not reflect a statistically equivalence between the detection of c and a.
Yes, I mean for BCC and BCT martensite. The c/a is approximately 1.08 for Fe-1.8C high carbon steel (see the attached figure 2.1). When the martensite structure deviates from the BCC strucuture, i.e. BCT structure, the detection rate gradually increases with the c/a value (carbon content).
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