You should try using acetic acid 25% or HF 0,5%

I belive that etching could only show the coarse insoluble precipitates which have no effect on precipitation hardening. To observe fine coherent precipitates you need TEM

Thank you very much, dear Hernandez

Thank you very much, dear Tarasov

hello Sajjad

I hope so that you look at ASTM E 407 to find adequate etchant for aluminium alloy.

I agree with Mr.Tarasov that only coarse precipitates can be seen at OM.

Wish you luck to find precipitates