Al1100 foil elongation loss after 160C soak

[jl2021]

I'm running room temperature tensile tests (ASTM E345-16) on 25um, 50um, and 75um H19 Al1100 foils before and after going through a relatively mild 1 hour @ 160C thermal treatment. As expected, there's a small decrease in strength (similar to the "Recovery" section here:

http://www.totalmateria.com/Article139.htm)

BUT elongation is dropping from 3% to <1.5%! I've not been able to find any explanation or observation of this behavior in literature and I can't find any problems with my test or sample prep. Heating to 300C still results in expected annealing behavior.

Is anyone familiar with this type of behavior in foils and willing to share some insight or point me in the right direction? My application will need to withstand short durations at 160C so this could have a large impact on our design.

Thank You!

 

[WKTaylor]

First...

How thick is Your foil and what specification?

How is Your Your foil cleaned prior to testing? How do You VERIFY it is cleaned to bare aluminum?

Are You testing in 'air' or 'combustion-air' or an 'inert-gas atmosphere' or in a 'vacuum'?

What will be the real-world environment for your foil?

What foil configuration/loading/fixity?

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Compositepro]

The foil will have a very significant oxide layer, relative to the foil thickness. The oxide layer is very brittle and will crack as the aluminum stretches.