The best etching method: Electroetching in HBF4 soution (5 ml HBF4 (48%)+200 ml Water). However You must provide good contact with the electropolisher (conductive resin is not good). I drilled the resin and used a crocodile clip to ensure proper contact. The next step involves electroetching 3x25 sec in 15 or 25 V. After that you can conduct observation in a light microscope equiped with a polarizator addon.

I have not used it myself, but ASTM E 340 recommends Flick's reagent on a 180 grit ground surface for 2XXX aluminium alloys.

BR Jacob

I have checked Flick's reagent today and the problem remains the same. In case of precipitation hardened alloy (T6) it works fine, but the grain boundaries in annealed material (O) are not revealed.

For structural examination of aluminum alloys u can use, HCl, HNO3, HF, which are often called Keller's reagent.

Perhaps of some interest to this query ─ On suggested etchants for Cu─Al alloys: https://www.researchgate.net/post/what_are_the_etchants_to_be_used_for_specimen_preparation_CuAl_based_shape_memory_alloys

I did a little looking around at different etchant-manufacturer and found this database which could be interesting for you:

http://database.metallographic.com/pace-etchant.php

Their first suggestion for Alu 2XXX for microscopic examination is Graff and Sargent, but there is a long list of possibilities.

Keller's reagent

I have been thinking about Graff and Sargent reagent, but unfortunately I do not have chromium (vi) oxide right now and I have to buy it in the coming weeks.

Today I have made some tries with 10% phosphoric acid and also with 1% sodium hydroxide but it seems to be a dead end. I still have to check some of these etchants from website posted by Jacob (nice database btw).

Please guys, stop writing about Keller's reagent - at the begining I said that it does not work.

You can try electrolytic etching with Barker's reagent, observe in polarized light.

Michal

use 0.5ml HF + 100ml H2O for about 45 sec...

you can also try 3m HF + 100ml H2O with varying times...

The best etching method: Electroetching in HBF4 soution (5 ml HBF4 (48%)+200 ml Water). However You must provide good contact with the electropolisher (conductive resin is not good). I drilled the resin and used a crocodile clip to ensure proper contact. The next step involves electroetching 3x25 sec in 15 or 25 V. After that you can conduct observation in a light microscope equiped with a polarizator addon.

Robert

AA2519 alloy is little temperamental. You try etching with Keller solution slightly warm with adding few mm more HNO3 to give you good view of GBs.

Dr. K

Normally Keller's reagent is most suitable for AA2xxx series. If you are unable to see the grain boundaries, You can try with electrolytic etching, which will provide better visibility.

Add more HF to the present Kellor's reagent to improve the GB visibility.

Oo

Keller agent should work, but if, not add little more HF and HNO3, warm it 50C and swab the specimen, wash it with acetone and then ethyl alcohol, dry it and examine under microscope.

Dr. K