what is overage condition, 2000/7000 series aluminum

[dho]

one big customer prohibits the use of 2000 and 7000 series aluminum alloy unless it is in overage condition. what is overage condition? what will be the condition designation?
thanks.

 

[TVP]

For 7075 and 7050, the T7 (or derivatives like T72, T7351, etc.) temper is solution treatment + overage. Instead of peak aging to maximum strength, overaging uses a somewhat higher aging temperature and produces somewhat lower strength, but improved ductility and fracture toughness. The T7 condition improves resistance to stress corrosion cracking and corrosion fatigue. A Google search will return many thousands of hits on this subject, but here are two documents that you might find useful:

http://www.keytometals.com/Article17.htm

http://projects.battelle.org/mmpds/ASIP02_paper_v7.pdf