Re: Analysis of aluminum alloy sample Aurora TX

On Feb 2, 9:33 pm, anon45...@xxxxxxxxxxxxxx wrote:
ASSESSMENT COMMENTS ON METALLURGICAL ANALYSIS AURORA, TX ALUMINUM
SAMPLE
Anonymous, PA, 2008

1.1 Introduction
In 1973, samples from a mass of aluminum were sent by John F.
Schluesser to several metallurgical labs for analysis. >
snip


2. DISCUSSION
Aluminum alloys containing significant concentrations of Fe have been
prepared and stuided in the laboratory at least since 1916[1].
Precipitates of the AlFe3 intermetallic compound were identified in
these alloys as early as 1919[2]. By the mid 1970's there were
several hundred papers in the literature concerning Al-Fe as an alloy,
owing to its interest as in intermetallic forming system[3], high
temperature structural applications, and a creep-resistant high
temperature conductor[5]. Such alloys consist of an aluminum matrix
into which are dispersed iron aluminide particulates, that form a
creep resistant microstructure enabling it to maintain structural
integrity at elevated temperature[5]. The class of structural
intermetallics compounds that includes iron aluminides (Fe3Al, FeAl),
along with related systems nickel aluminides (Ni3Al, NiAl) and
titanium aluminides (Ti3Al, TiAl) posess many attractive properties
for high temperature structural applications. The aluminum rich
composition favors formation of protective Al2O3 in oxidizing
environments, low density, high melting points, and high temperature
strength[6], and it is predicted they are the most likely to replace
superalloys in future applications. A key challenge is overcoming the
brittleness of pure single phase intermetallics at low temperatures
and developing improved fabrication techniques.

Given the low solubility of Fe in Al and their widely different
melting temperatures, producing a bulk alloy of these materials is
difficult. An overall composition of Al0.95Fe0.05 can be prepared via
solidification from a high purity melt above 700C containing Al and Fe
in these quantities, or via powder metallurgy whereby Fe and Al
particles are milled together in a mechanical attrition process, then
sintered to form a bulk compact. In the metallurgical analysis of
1973, it is mentioned that the sample has large grains with needle-
like iron-rich strucutures. This is suggestive of a solidification
process where Fe-rich liquid segregates ahead of dendritic or cellular/
columnar solidification and forms extended iron-rich strucutres and
precipitates in the interdendritic/intercellular spaces. Powder
metallurgical microstructures typically would consist of a more
equiaxed microstructure with small Al grains interspersed with compact
AlFe or Al3Fe intermetallic particulates.

SNIP

3. CONCLUSIONS
Technical
From the available metallurgical analysis documentation of 1973, it
appears
· The sample is an alumunum matrix composite with overall composition
Al0.95Fe0.05, with extended or needle-like Fe-rich structures, likely
an iron-aluminide intermetallic phase.
· Given the composition and microstructure this sample must have been
produced in a well-controlled metallurgical process, such as in a
laboratory.
· The capability to produce this material has existed since 1920, but
this composition would not have been widely available until sometime
after World War II. By 1973 it would have certainly been available to
someone with R&D connections in the aluminum or aerospace industries.

Relation to location of discovery
· The claim is that this metal sample was recovered from an 1897
'debris field' in Aurora TX, but there is absolutely no proof that
this sample is truly from this location. The sample discovery was not
properly documented and changed hands several times thus making it
useless for further study.
· Although Al-Fe alloys have been produced in research quantities
throughout most of the 20th century, they are not available
commercially, and therefore highly unlikely to have been deposited by
normal human activity in a rural area such as the location alleged.
· If the sample were truly collected from a debris field (for which
there is no proof) it is almost certain that additional ...

read more >>

I think you are making WAY too much out of finding that someone had
some pieces of aluminum alloy analyzed and found only iron by SEM-EDS
and X-ray fluorescence. If I had not found your other post I would
have assumed that you were pulling our legs.

Now, if you go to the Aluminum Association and look up their wrought
alloy composition tables (the Teal Sheets) at:
http://www.aluminum.org/Content/NavigationMenu/The_Industry/Industry_Standards/Tealsheets2006.pdf
then you will find that there is a whole series of 8XXX iron
containing alloys registered for commercial use. See page 20 of the
pdf file (or page 12 of the printed version). Alloy 8079 was
registered in 1969. It contains 0.7 to 1.3% Fe and 0.05 to 0.30% Si.
Alloy 8021 (registered in 1992) contains 1.2 to 1.7% Fe and 0.00 to
0.15% Si..

The 8079 and 8021 alloys are used commercially for aluminum foil in
packaging applications.

See "Industrial Development of Non-heat Treatable Alloys"
http://www.materialsaustralia.com/Materials_Forum/Vol28/INV%206.pdf

and also see "The Combination of Film & Foil - Still Up To
Date" (which mentions 8006, 8014, and 8079)
http://www.alucontainer.org/media/Film_and_Foil.pdf

and also Alcoa European mill products catalog (which mentions 8006,
8011, and 8079)
http://www.alcoa.com/mill_products/catalog/pdf/specialties/en/foil_EN.pdf

Pittsburgh Pete

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