Letter 32031

Suitable etchant for al6061  

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I am a Final year undergraduate student in Singapore and I am working on Al6061-T6 alloy. I am having problems in getting optical microscopy (my objective is to get the grain size of the alloy). I tried different etchants (Kellers, Poultons, NaOH solution, HF dilute solution) and electropolishing (5 ml HBF4 (48%)+200 ml Water) but I am not having success, in return I get a micrograph which contain lots of black particles and "bubbles" in the picture for every etchants I tried.

Before doing any processing (ECAE), I preheat the as received al6061 to 415 degree for 3 hr and then cool down to RT.(I wonder if my heat treatment is the cause of the problem, can anyone tell me?)

I would like to know which is the best and suitable etchant and step by step procedure for this case? Thank you very much if you can reply me asap. I really need your help.

p/s: if anyone is interested in my micrograph, which I don't know what is that in the picture, it is here.

Regards,

Thomas ong
NTU, SG - Singapore

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