2024-T4 vs 2024-T351 per qq-a-225/6
2024-T4 vs 2024-T351 per qq-a-225/6
(OP)
My customer has removed 2024-t351 per qq-a-225/6 as an alternative temper to 2024-t4 citing only "property discrepancies". Does anyone know what the discrepancies are?





RE: 2024-T4 vs 2024-T351 per qq-a-225/6
T351 is a plate extrusion form, T4 not (rolled plate?)
strength-wise there isn't much in it, about 5% (T351 is stronger than T4)
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RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
i doubt there's much in it, i'd be looking for their engineering buy-off ... is it an alternate material on the drwg ? is there some production paperwork (RNC?) for the change ?
another day in paradise, or is paradise one day closer ?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
another day in paradise, or is paradise one day closer ?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
clearly the substitution can be allowed (since the drwgs allowed it for 30 yrs).
however, someone recently decided it wasn't a good substitute, for "property discrepencies".
but now the question has to be "what were these discrepencies?" and "why were they so significant as to change the drawing?" and "why can we accept these discrepencies now?"
this is more involved than this forum permits.
another day in paradise, or is paradise one day closer ?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
another day in paradise, or is paradise one day closer ?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
I suspect that MMPDS-* and AMS-QQ-A-225/6A spec mechanical-allowables differences between -T4 and -T351 are what drove this revision.
However, I-too am baffled by the change none-the-less, since -T351 [mechanical] allowables are equal-to, or [generally] superior-to, -T4 allowables [especially as section thickness increases]... and all other properties are generally identical [e, E, density, strength-VS-temperature, KIscc, KIc, etc]. Unsure about fracture mechanic properties [dA-dN etc].
NOTE.
As a rule I would NOT specify any 2XXX-T3xxx or -T4xxx Temper due to very poor KIscc [SCC] and EXCO ratings. Specify 2XXX-T8xx or -T62 temper for Higher mechanical allowables and MUCH better environmental durability, where possible [and as-allowed by stress/DADTA weenies].
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant û "Orion"
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
another day in paradise, or is paradise one day closer ?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
I agree 100% with Your statement RE sheet metal, thin extrusions, thin bars, etc...
However, MIL-STD-1568 TABLE I. Rating for resistance to SCC aluminum alloys in the short transverse grain direction (STDG) , MMPDS-08 Table 3.1.2.3.1(a). Resistance to Stress Corrosion Ratingsa for High-Strength Aluminum Alloy Products, several other references [ASMH, in-house design documents, etc], and personal/field experiences clearly indicate significant SCC* and EXCO** problems with rolled plate, rod/bar [rolled and/or drawn], extrusions and forgings. In general the -T3 and -T4 tempers should be restricted to as-wrought [rolled, drawn, extruded, etc] stock material thicknesses of less than 0.249-inches to minimize potential for SCC and EXCO.
*SCC = stress corrosion cracking.
**EXCO = exfoliation corrosion
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant û "Orion"
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
"a The T4 temper is obsolete and should not be specified for new designs." under the AMS 4120 and AMS-QQ-A-225/6 column.
Shouldn't the design originator be able to tell why the substitution was withdrawn?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
MIL-HDBK-5A [1966, first time QQ-A-225/6 appears]
TABLE3.2 .3.O(g)D. Design Mechanical and Physical Properlies of 2024 Aluminum Alloy (Bor, Rod, and Wire); Rolled, Drawn or Cold Finished; Drawn Tubing
Mechanical allowables [S-basis] for '-T4 or -T351' are identical [same collums]
However, in MIL-HDBK-5B [1973] the [S-Basis] mechanical allowables for QQ-A-225/6 -T4 and -T351 have been separated and minor differences are apparent. -T351 is generally equal-or-superior-to -T4... EXCEPT for Fbru [very odd/unexpected/minor]. This 'difference' [-T4 VS -T351] generally tracks true from 5B~thru-MMPDS-08.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
T4 carries the "obsolete for new design note" mentioned above. Both T4 and T351 have the caution about poor SCC rating (in the LT direction).
On the face of it, T351 is a reasonable substutite for T4.
another day in paradise, or is paradise one day closer ?
RE: 2024-T4 vs 2024-T351 per qq-a-225/6
On the other hand, I have seen similar situations while working on legacy programs like the Space Shuttle. I recall a situation where NASA asked the company I worked for to manufacture some spare parts that had not been produced for 20 years. Some of the process specs listed on the old paper drawings were obsolete, and there were no vendors still qualified to perform the work required by the old specs. So I had to create lots of paperwork to cover the use of current process specs in place of the obsolete ones. It was a huge headache.