2024-T3511 vs. T42 1

Hope this make sense...

2024-T3 is a 2024 OEM temper.
The raw/fresh extrusion is solution HT... then quenched to attain the 'W**' temper... then the extrusion is naturally aged to attain the -T3 state. The strict controls on fabrication process HT generally mandate an OEM [or equivalent/certified-aluminum mill] do this work. Some distortion/straightness irregularities... and to a degree facture toughness and EXCO resistance... and other subtle properties are 'uncontrolled'.

2024-T3511 is a 2024 OEM temper.
The raw/fresh extrusion is solution HT... then quenched to attain the 'W**' temper... then the extrusion is strain-stretched/straightened while in the 'W**' temper... then naturally aged to attain the -T3+511 state. The strict controls on fabrication process generally mandate an OEM [or equivalent/certified-aluminum mill] do this work. This temper state is generally preferred due to inherently high straightness and freedom from distortion... which manufacturers prefer for long-lengths.

2024-T42 is a 2024 'user/shop' temper.
The raw extrusion [any temper] is solution HT by a user/shop... then quenched to attain the 'W**' temper... then naturally aged to attain the -T42 'user' temper, due to generally 'poorer shop controls' on all HT variables. The -T42 temper [properly accomplished] has pretty-much the same mechanical properties as '-T3' temper including allowed distortion/straightness irregularities... and to a degree poorer facture toughness and EXCO resistance... and other subtle properties are 'uncontrolled'. Generally this temper is reserved for parts intended to be severely formed by a shop while the alloy is in the unstable 'W**' temper

W** is an transient/unstable temper... and is a very limited period of time, when severe deformation will not detrimentally affect grain structure after the forming and subsequent transition from W-to-T. This 'W' state can be 'frozen' for a few days in the quenched part is immediately placed into a very cold -40F environment... or longer if held colder [-100F]... allowing forming-fabrication delays... BUT, with VERY CLOSE temperature monitoring.

Summary. The -T42 [extruded profile] temper is equivalent to a -T3 temper... and both are somewhat inferior to the -T3511 temper.

What bothers me the most is that a temper substitution like this... -T42-user for -T3511-OEM... appears to have been unapproved by your company and may in-fact be unsuitable for the intended application... or maybe NOT. However, the acceptability of -T42 ILO -T3511 must be based on a technical rationale VS the intended end-use.

CAUTION1. As I understand it... 'BAC' implies a 'Boeing' extrusion[?]... so, for Boeing use, this will probably receive a thumbs-down without prior engineering waiver/approval. IF a this deviation is formally allowed... then 'OK'... if not, then these raw extrusions should be rejected back top the supplier. Period.

Regards, Wil Taylor
o Trust - But Verify!
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", HBA forum]
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What could be the potential consequences if we said “it’s fine” and used T42 instead of T-3511? > YOU likely cannot say it is fine. It is a non compliance to the BAC and unless you have full MRB authority, which I doubt, then you cannot disposition the material. If you somehow get enough data to somehow attempt to justify using the material it will need to go to your customer for approval BEFORE you use it.

does their certificate say it is T3511 ? or does it say "at the end of a bunch of processes the tensile strength is not incompatible with the T3511 spec" ?

I think there is a standard way to achieve T3511 and it seems to me that these guys have done some non-standard way (if they say they have achieved T3511).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

Thank you everyone for the feedback!

Our end customer is the Air Force and there are no temper substitutions. I’m glad to see I’m not the only one saying what the supplier gave us isn’t ok.

We’re going to scrap the parts and investigate the suppliers other cert.

Edit: To clarify, our supplier certed the temper to T-3511 but the process at the HT facility said “F to W” and then listed only a quench under their process. Seeing as that was the only evidence given it made me question what temper our supplier had really ordered.

WKTaylor, I’ve seen your contributions here for a while and your answer is exactly what I needed. Thank you for the information — your reply is as invaluable as always.