Until now I did not work with the map component of Tango (Channel5, Oxford Instr.). Therefore a short question: attached are two images displaying the recrystallized fraction of a martensitic steel. Both maps are based on the same measurement but different orientation determination techniques have been applied: HT...Hough transformation, DS...pattern matching. In both maps the same settings are used (to separate subgrains: 0.5°, to separate grains: 5°). Does anybody know how these presentations are derived?
Prof. Nolze,
The two images look very different, it is quite unusual. Do the regular orientation maps (with Euler angle colouring/IPF colouring) also look very different? If so, perhaps some setting in one of the two modes (HT vs DS) is off. Could you please indicate where the options for orientation determination techniques (HT vs DS) are available?
As for the Recrystallized Fraction component, it returns the number fraction (unlike areal fraction as in some other packages) of 'recrystallized grains' (as opposed to 'deformed grains'). The 'recrystallized' grains are identified following this procedure*:
(1) Identify and reconstruct grains (based on the misorientation angle specified, here 5o)
(2) For each grain, determine the average misorientation between points.
Now for one grain:
(3) If this average value is less than the angle for subgrains, i.e. here 0.5o), that grain is considered 'deformed' and coloured red by default.
*largely sourced from the Tango manual.
Dear Aashranth B., the orientation maps look practically identical. HT means orientation determination using Hough transform (standard indexing in any EBSD software), DS stands for orientation refinement using pattern matching. With DS the orientation precision is only about 10 times better than with standard Hough transform.
Your explanation is reasonable, many thanks.
I have to think what does it mean... Again, both representations are based on the same experiment. I only stored the patterns and reanalyzed them (obviously considerably better than EBSD systems do). From my point of view it seems that an essential part of the recrystallyzed microstructure is recognized as deformed. This is certainly a result of the presettings. As you see, I reduced the minimum angle to 0.5 which is absolutely no problem for the refined data, but deadly for the original data which are characterized by much more orientation noise/spread/diversion.
Anyway, you helped a lot (although I deeply apoligize that I did not search for the Tango manual...it should be somewhere)
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