We forge a 7175 reverse extrusion on the order of 2.5" thick which gets heat treated to the T74 condition. The requirements are 76k/66k UTS/YS in the longitudinal direction and 38% min IACS (AMS 4149). I have been playing around with the heat treatment, namely the first age temp (225F-250F), second age temp (325F-350F), and cycle times for both, but I have not yet obtained a good balance of properties - I can get either IACS to pass or strength to pass, but not both simultaneously. On several samples I was just barely passing on YS/UTS/IACS but not by enough margin that I'd consider it a repeatable process.
I know this is a particularly tricky temper condition and some people resort to exotic heat treatments like 3 or 4 step ages to fine tune their properties - does anyone have any suggestions?
Appreciated,
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Sean Piper
Product / Process Metallurgist
Ellwood Texas Forge Houston
Houston TX
(713) 434-5138
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