Print

[Ric Gillespie]

We're getting some interesting results from the metallurgical testing being done by Lehigh Testing Laboratories but we need historical information about 24ST ALCLAD to understand the significance of what we're finding.  One document that might be helpful is "Ten Years' Service Experience with Alclad Materials in Aircraft" published in S.A.E. Journal, Vol. 44, No. 5, May, 1939.

Can anyone help us find a copy?

[Bruce Thomas]

According to this webpage, it can be downloaded for $25.

[Ric Gillespie]

According to this webpage, it can be downloaded for $25.

Got it.  Thanks.

[Martin X. Moleski, SJ]

According to this webpage, it can be downloaded for $25.

Got it.  Thanks.

The Forum is off its feed today.

That took almost a whole hour!

[Ric Gillespie]

The document is of some use but we're still looking for a detailed history of the evolution 24ST, the "core" alloy in 24St ALCLAD.

In 1941 the Federal specification for 24ST sheet was QQ-A-355.  Of course, that spec has been superseded several times since then.  I can't find a copy of the original QQ-A-355.

After reviewing the current spec, I'm not sure that finding QQ-A-355 will help us.  The spec doesn't include the percentages of elements in the alloy and that's what we need.

[Edgard Engelman]

Please find as an attached file an interesting document about the composition of ALCAD particularly Table 1

Edgard

[Ric Gillespie]

Please find as an attached file an interesting document about the composition of ALCAD particularly Table 1

That's just what we were looking for.  Thank you.

[Jeff Lange]

Now, see Marty-that only took an hour and 33 minutes! It IS Saturday you know! :-)

[Martin X. Moleski, SJ]

Now, see Marty-that only took an hour and 33 minutes! It IS Saturday you know! :-)

In other words, it is a great day to donate time to the Earhart Project!   

[Frank Hajnal]

The document is of some use but we're still looking for a detailed history of the evolution 24ST, the "core" alloy in 24St ALCLAD.

In 1941 the Federal specification for 24ST sheet was QQ-A-355.  Of course, that spec has been superseded several times since then.  I can't find a copy of the original QQ-A-355.

After reviewing the current spec, I'm not sure that finding QQ-A-355 will help us.  The spec doesn't include the percentages of elements in the alloy and that's what we need.

I don't know if this will help, but page 59 of the 1941 edition of Alcoa's Aluminum in Aircraft, which is available on Tighar's Web Site (http://tighar.org/Projects/Devastator/photographs/AluminuminAircraft.pdf) provides the Cu, Mn, and Mg content of 24S at that time.  Comparing those values to the current ones as listed in an Alcoa Data sheet (http://www.alcoa.com/mill_products/catalog/pdf/alloy2024techsheet.pdf), it looks like there hasn't been a change in the content of these three elements over time.  Shouldn't the major chemical components of 24S, or any alloy, remain the same over time? Changing the chemical composition of the alloy would result in a new alloy, wouldn't it ( I'm not a metallurgist, so I don't know for sure)?

It would seem to me that it is the trace chemical components of Alclad that might be indicative of provenance, because the manufacturer wasn't trying to fix them within certain limits.  Trace element composition have for instance been used to trace things like marble sculptures, and megaliths back to their quarrying locations.   However the problem there would be that it would be a major project to try to figure out whether some particular trace element is useful in indicating something useful about the aluminum provenance (e.g., when manufactured, where manufactured, where the Aluminum was mined, etc.).

[Martin X. Moleski, SJ]

From a diligent reader:

Alloy 2024 was introduced by Alcoa in 1931 as an alclad sheet in the T3 temper. It was the first Al-Cu-Mg alloy to have a yield strength approaching 50,000-psi and generally replaced 2017-T4 (Duralumin) as the predominant 2XXX series aircraft alloy.

http://www.alcoa.com/mill_products/catalog/pdf/alloy2024techsheet.pdf

Al-Cu-Mg alloy
http://keytometals.com/page.aspx?ID=CheckArticle&site=ktn&NM=240

[Edgard Engelman]

It is clear that what you need is the description of US patent 1,924,729 to L. J. Weber (1933). This is I think the beginning of patenting for the US style of ALCLAD. I could not find it online, although many publication refer to this patent.

However find as an attached file patent 2,240,940 assign to Aluminum Company of America dated September 1940 which gives various experimental compositions current in think in 1939.
An important part in this last patent is the text "a small amount of one or more of the grain refining elements titanium, boron, zirconium, molybdenum, tungsten, cobalt, chromium, and vanadium, avoid to a large ex tent the above named disadvantages usually associated with aluminum base alloys containing substantial amounts of zinc".
If one of these elements is present in the sheet of metal you have in possession, it is likely that it can not come from a piece of metal commercially available in 1937

Edgard