Dear Dr. Alireza Ahari ,

I suggest you to have a look at the following, interesting technical note:

-Metallographic Etching Technical Information by PACE Technologies

Available at: https://www.metallographic.com/Metallographic-Technical/Metallography-Technical-Etching.htm

A tip: if Keller's solution seems too aggressive for your Al alloy and you can't manage the attack time ... try diluting it, it might work.

Best regards, Pierluigi Traverso.

Dear Dr. Alireza Ahari ,

I suggest you to have a look at the following, interesting technical note:

-Metallographic Etching Technical Information by PACE Technologies

Available at: https://www.metallographic.com/Metallographic-Technical/Metallography-Technical-Etching.htm

A tip: if Keller's solution seems too aggressive for your Al alloy and you can't manage the attack time ... try diluting it, it might work.

Best regards, Pierluigi Traverso.

Dear Alireza

I had this problem many times. I suggest using the etchants explained thereunder if you have already tried various compositions and etching time using Keller solution. I assume you would like to see the grain boundaries within the interface. If so, you had better etch the layers separately since any layers have distinct compositions, making it hard to reveal the grain boundaries with just one etching process.

Concerning etchant for AA6063 aluminum, try to use the following solution due to its mg and si elements.

Methanol: 25ml Hydrochloric acid: 25 ml Nitric acid: 25ml Hydrofluoric acid: one drop approximately.

Pierluigi Traverso thanks so much for your article recommendation. I have already used diluted Keller but there is no effect. I would try the following instruction that you mentioned finding a proper solution.

Regards