I have 70 percent cryo-rolled 2219 samples but i am not able to get good scan from EBSD,what should I do?
It is most likely the high dislocation density introduced during cryorolling that causes the bad pattern quality in your EBSD scan. Perhaps you have achieved nano-structured material? You can try to minimize the interaction volume. However, you will most likely have to find alternative ways for crystallographic orientation analysis of this material. You may also anneal the sample slightly but this probably is contrary to the subject of your study.
Hey Pal,I tried to reduce interaction volume nd step size also but with no avail.Also I don't want to anneal the sample.Thanks for answer.
Hi, do you get a good distinctive patterns on individual points? just try to point on the sample ans see what is on the fosforscreen (EBSD camera) . If the software cant identify the pattern clearly as FCC in this case, scan will probably not go well.
As for he original question-- colloid silica should work OK, electroplating is a nonsense, so I suppose you meant electro-polishing which, when done properly may be better than colloid silica since it is nearly impossible to get rid of the several tens manometers big SiO spheres. Some always stick to the surface and you must remember this when feeling like you have found new sphere-shaped precipitates in your material :-)
And one thing you may try is channeling contrast wit BSE detector.. much faster than EBSD and gives you information about crystallinity or deformation state as well. Just you don't get all the subgrain and orientation fancy stuff.
Hello sir,Thanks for your time.
1.No i am not getting good pattern at distinctive points.
2.I wanted to ask about electro-polishing not electroplating(it was typo).
kindly suggest further.
Dear Aditya,
There may not be a clear winner between the two; it is best that you try both and see what works better. Some people even do both.
However since you are not getting good patterns anywhere, I suggest you spend more time on mechanical polishing rather than the finishing step (colloidal silica/electropolishing). Are you polishing with 1um or finer diamond suspension? If you can, it is highly recommended to polish using 0.5um suspension for 25-30 min at a low speed (50-60rpm). If not, do the 1um polish for atleast 20min.
Doing a long colloidal silica polish can cause silica particles to get embedded in your specimen. On the other hand, if your specimen is not microscopically 'flat', electropolishing won't flatten it further, it will simply remove one layer, preserving some of the ups and downs.
So it could be a good idea to do a long, slow diamond polish (ensure complete flattening), followed by electropolishing with 10%-20% perchloric acid (in ethanol/methanol). Be careful of the time and bath temperature, you could end up with pits if you polish too long/with an insufficiently cool bath.
Dear Aditya,
EBSD requires a strain free surface. Your sample is expected to have heavily deformed grains which are difficult in indexing. Here are few tips you can try.
Basic step : Take care of basic metallographic polishing i.e. from coarse polishing paper to diamond polishing. It is suggested to go it 0.5micron diamond polishing. Make sure to get a flat and scratch free surface.
Electropolishing: It is fast process . However proper solution; flow rate, current and time has to be optimized. You might end up in over polishing of sample. Since your sample is highly deformed, it might result in formation of pits i.e. the highly deformed fine grains may be eaten away by solution. So a low value of the above parameter is suggested. You might find in literatures.
Colidial Silica : It is suggested for your material. However it consumes a lot of time and effort. Here is one of the best method. Initally you polish the sample with colidial silica with running water for 25-30min. This results in formation of some bluish layer on sample. In order to remove it, futher polish the sample just with water for about 40-45 min more.This should give you best result.
Note:Dont let the colidial silica dry. This can result in formation of new sratches. So keep water always ON.
Apart from these you can try the other techique like Vibratory polishing or Ion beam milling.
All the best
Perhaps you can pick up a few ideas here:
Webinar: "Quantitative Characterization of Nanostructured Materials with Fast TKD Measurement".
They use a tranmission detector in the SEM for Kikuchi Pattern measurements. This could be an efficient way to characterize nanostructured material if you don't have a TEM at your hand.
https://www.bruker.com/service/education-training/webinars/eds-ebsd-and-micro-ct-for-sem/quantitative-characterization-of-nanostructured-materials-with-fast-tkd-measurement.html
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