Hello!
I have Al 6082 samples (strongly deformed by extrusion and partially recrystallized) and I would like to do an EBSD analysis of the recrystallized zone and have already tested the following final preparation steps (after about 25min colloidal silica polishing):
- HF etching
- elektropolishing
- about 24h in vibromet
- only ultrasonic cleaning with ethanol, after cleaning with hot water
- instead of colloidal silica, I also tried aluminium oxide (sample was etched)
For grinding (up to 4000 grit size) and polishing (6µ - 35min, 3µ - 40min, 1µ - 40min), I used the lowest possible force.
But the result is always the same, I don't get kikuchi patterns.
Does anyone have an idea what the problem might be?
Thank you very much for any help!
It can be due to several different issues. First, you may have got an amorphised metal so you can't get good Kikuchi with any treatment. You may check that with x-ray powder diffraction (without powder preparation, you just need to see the peaks). Second, Al is tricky and it may have very small grain size, if you're using tungsten gun grains under 100 nm may give you no distinct EBSPs due to overlay (try 10kV and low current for better focus, but it still be a very hard for small grains).
Third, if you have a very scarce steps while polishing (e.g. 600 grit and then silica) you may still have influence of previous steps due to thick amorphization layer at grinding.
Also you may prepare thin section with FIB to check whether your absence of patterns is due to bad sample preparation. This method can be mentioned an universal standard.
Vladimir V. Shilovskikh thanks for your answer!
To 2: we work with a FEGSEM, and the grain size is over 100nm (see light microscope pictures of relevant region - Barker etching), so I think this is not a problem.
To 3: I used several polishing steps always lasting longer: (6µ - 35min, 3µ - 40min, 1µ - 40min, 25min OPS, 23h vibromet).
I'll see if we can check with x-ray diffraction.
Best regards
Markus
Do you see the same image in FSD?
There also always is a possibility of wrong Kikuchi acquisition settings which i hope you did avoid. You may check it placing known sample (e.g. steel with guaranteed diffraction) near studied Al.
Also once I had an unique situation where sample's structure was highly damaged with electron beam and i got data only at very high speed, and the surface was amorphized after that. That one also can be checked with 10kV and low dwell times, but it would be highly improbable for metal.
Also i may suppose very fast oxidation forming superfine crystals of oxide if you are not fast enough. This can be seen on low-kv edx spectra if you have it.
And there i give up because can't guess anything else.
Do you have access to ion beam etching facilities? We usually finish the "tricky" Al samples with some Ar+ ion beam etching.
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