ORNL_ANALYSIS_OF_AN_ALUMINUM_SPECIMEN.pdf

SYNOPSIS:
Analysis of an 
Aluminum Specimen
Prepared by Oak Ridge National Laboratory (ORNL) 
for the All-Domain Anomaly Resolution Office (AARO)

Synopsis: Analysis of a Aluminum Specimen
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Executive Summary
The All-Domain Anomaly Resolution Office (AARO) sponsored a series of measurements on drill 
shavings and a small sectioned piece from a metallic specimen. Oak Ridge National Laboratory 
(ORNL) independently performed multiple, cross‑validated measurements showing that the 
material is a conventional, near‑eutectic aluminum–silicon alloy (i.e., an ordinary aluminum 
alloy made for common applications). Its chemistry, microstructure, internal porosity, and lack 
of radiological signature are consistent with decades of known industria…

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1.	 Overview
AARO is congressionally mandated to investigate  unidentified anomalous phenomena (UAP) incidents 
and publicly report its findings. AARO sponsored a series of measurements on a metallic alloy composed 
of primarily aluminum and silicon, claimed to have association with a UAP in or around 1995 and further 
asserted to have nonstandard composition. AARO secured science and technology partner ORNL, one of 
17 US Department of Energy National Laboratories, to independently assess and perform thorough char‑
acterization studies on samples fr…

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2.	 Methods 
To identify the alloy family and probe claims of unusual behavior, ORNL combined multiple complemen‑
tary methods that analyze different size samples with cutting-edge precision. 
2.1 Bulk chemistry/elemental makeup — Portions of the shavings were dissolved and analyzed by 
inductively coupled plasma (ICP) optical emission spectroscopy (OES) for major and minor elements 
and by high‑resolution ICP mass spectrometry (MS) for trace elements. The bulk piece was analyzed 
by glow discharge (GD)‑MS to cross‑check the overall composition. Chem…

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matrix, needle- and block-shaped silicon, Fe/Mn‑rich intermetallics, and occasional Cu/Mg‑bearing 
precipitates. Small Pb‑rich pockets are present but scarce in both the bulk and shavings, most likely 
representing incidental impurities commonly seen at very low levels in industrial feedstocks and 
tooling. This indicates that the alloy’s chemical identity is not an artifact of machining: the bulk interior 
matches the chemistry and phase assemblage inferred from the shavings.
Figure 2. An individual shaving on a carbon sticky tape background and SEM…

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Figure 4. 20 kV electron beam, polished shavings sample. (a) Low-magnification concentric backscatter electron image 
showing a surface of one end of a shaving. (b) Area denoted in the yellow box of (a), showing multiple phases from the 
epoxy (black), matrix (dark), and various intermetallics and second phases (medium gray to white). (c) False-color x-ray 
map denoting the major phases; marked areas are quantified. (d) Quantitative X-ray mapping of the major and minor 
elements. The metal atoms’ speckle in the epoxy region is noise. Rough compositio…

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The bulk specimen’s interior contains clusters of winding, interconnected pores—a typical pattern of 
interdendritic shrinkage that occurs as castings solidify and contract. The large pore size (from 0.5 
mm to over 1 mm) suggests a relatively slow cooling rate, which is typical of thick‑section or larger 
molds. Together, the porosity, intermetallics, and Si features are consistent with a sample that was 
gradually cooled from a large cast.
5 mm
YZ
XY
Figure 5. Two renderings from the XCT data. The purple surfaces are the pores. 
Light blue lines ar…

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3.4 Gamma spectroscopy: No unusual signal emissions — Gamma spectroscopy results indicate no 
radioactivity emitted by the metal flake material. Background spectra were acquired for count times 
almost 50% longer than the samples. The resulting spectra were compared to background and 
found to be indistinguishable from background spectra when count time normalization was applied. 
No radioactive emissions were detected in any sample. Figure 7 shows the results from one of 
the metal flakes, which is representative of the other metal flake spectra. Th…