ORNL: 알루미늄 시편 분석

ORNL Synopsis: Analysis of an Aluminum Specimen

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

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 industrial practice, specifically
falling within the profile of standard 300/400-series casting alloys that have been widely produced
since at least the 1970s.
AARO requested a technical analysis of a metallic specimen with claimed association to an unidentified
phenomenon occurring over central Ohio in the mid-1990s. ORNL was charged with evaluating specific
assertions of unusual sample composition. ORNL received three bags of drill shavings and one small
bulk piece of the specimen—integrating chemical assays, multiscale imaging, x‑ray spectroscopy, and
gamma spectroscopy to perform this evaluation.
ORNL found the sample exhibits the following qualities: (1) aluminum composition with approximately
12% silicon by weight; (2) standard second phases and casting pores; (3) features indicating slow-cool‑
ing, consistent with conventional large casting in a mold; and (4) no abnormal gamma emission. Nothing
in the data suggests novel physics or exotic origin.
Specifically, microscopy revealed silicon plates/needles, iron- and manganese-bearing intermetallic sec‑
ond phases, and shrinkage porosity—features that are typical of slow‑cooled castings. The sample’s
chemical composition shows no evidence of elements outside those expected for conventional alumi‑
num metallurgical engineering, and gamma spectroscopy showed no unexpected emission.
In conclusion, none of these data support claims of unusual characteristics. The evidence points to
ordinary, terrestrial industrial metallurgy consistent with parts used in (late 20th century) automotive,
aerospace, and consumer applications. These conclusions are robust for the samples provided and for
the methods described herein.
Synopsis: Analysis of a Aluminum Specimen 1

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 from the specimen, leveraging ORNL’s 80-year history of world-leading
materials science expertise.
Figure 1. Photographs of the received samples.
(Left) Metal shavings in their transfer vials.
(Above) The main mass material.
The central charge to ORNL was to investigate (1) the composition of the metal, (2) whether the chem‑
istry or structure is anomalous, and (3) whether it emits a gamma-ray signal. Drawing on established,
peer‑reviewed methods and side‑by‑side quality controls, ORNL found that the sample is a conventional
near‑eutectic aluminum–silicon alloy near the Al–Si eutectic composition.
A eutectic composition is an alloy that melts at a lower temperature than either of its individual compo‑
nents and typically exhibits superior castability and fluidity, making such alloys preferred for manufac‑
turing applications where shaping of parts is critical. Eutectic compositions are thus well understood
and common in manufacturing—details are documented on phase diagrams that show where an alloy
in liquid form transforms into separate solid phases simultaneously upon cooling. Specifically, the sam‑
ple in question can be best described as a eutectic aluminum–silicon alloy nearly, though not perfectly,
matching American Society for Testing and Materials (ASTM) designations A413.1/369.1.
In addition to finding no evidence of unusual elements or chemistries that would imply novel mecha‑
nisms, ORNL found no evidence of rapid cooling or gamma emission.
The use of multiple, independent methods (with calibration against recognized standards) reduces the
chance of a systematic error and increases confidence that these samples are representative of the
source part. Additional pieces from different locations of the original component, or access to manufac‑
turing records, could narrow the identification to a specific catalog grade and heat treatment, but such
data are not necessary to support the central findings reported here, which indicate no behaviors incon‑
sistent with ordinary cast aluminum.
Synopsis: Analysis of a Aluminum Specimen 2

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. Chemistry is the primary fingerprint
of an alloy; if an element were out of place or at an unusual level, it would appear here.
2.2 Structure from micro‑ to macroscale — Individual shavings and polished cross‑sections were
examined by scanning electron microscopy energy dispersive x-ray spectroscopy (SEM-EDS) to
visualize the distribution of elements and features such as grains and precipitates. X‑ray computed
tomography (CT) provided a 3D view of internal pores and their connectivity (i.e., casting features).
Structure reveals how a specimen was made—cast versus wrought, fast‑cooled versus slow‑cooled—
and whether it resembles known industrial practice.
2.3 Signal detection/monitoring — Gamma spectroscopy monitored three of the metallic samples for
a period of approximately two days. This technique is sensitive to a wide band of isotopes and low
levels of emission. This evaluated whether unusual signals were emitted from the metal.
3. Results
3.1 Chemistry: An Al–Si alloy — Results indicate that the Table 1. Bulk composition summary
sample is an aluminum–silicon (Al‑Si) alloy near the Al–Si (weight %). Values are rounded; trace
elements shown for context. Analyses
eutectic. The dominant elements are aluminum (~86 wt%)
of the bulk sample and shavings were
and silicon (~12 wt%), followed by iron (Fe, ~1 wt%),
compositionally consistent.
copper (Cu, ~0.37 wt%), magnesium (Mg, ~0.30 wt%),
zinc (Zn, ~0.20 wt%), and manganese (Mn, ~0.20 wt%). Instrument Element wt%
Several other elements (lead [Pb], chromium [Cr], nickel
[Ni], titanium [Ti], and gallium [Ga]) appear only at trace GD‑MS Al 86.10
levels (tens to hundreds of parts per million). These are
GD‑MS Si 11.90
the expected elements within common casting grades and
do not suggest exotic additives. The shavings and the bulk ICP‑OES Fe 0.97
sample had identical chemistry for all elements measured,
ICP‑OES Cu 0.37
by multiple techniques, within the analytical uncertainties
of the instruments. This chemical composition is consistent ICP‑OES Mg 0.30
with a near‑eutectic Al–Si casting alloy—conventionally
ICP‑OES Zn 0.20
used when designing molten aluminum to flow easily into a
ICP‑OES Mn 0.20
mold and reproduce fine details.
3.2 Shavings vs. cross‑sectioned shavings: Impact of drilling ICP‑MS Pb 0.04
changes — The shavings given to ORNL show folding
ICP‑MS Cr 0.03
tool marks from drilling performed before AARO acquired
the material. The undisturbed interior was exposed by ICP‑MS Ni 0.03
embedding the sample in epoxy, cross‑sectioning, and
ICP‑OES Ti 0.03
polishing. In the interior, ORNL observed a suite of phases
ICP‑MS Ga 0.01
consistent with standard cast Al–Si alloys: aluminum
Synopsis: Analysis of a Aluminum Specimen 3

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.
Machining marks
Folding
Figure 2. An individual shaving on a carbon sticky tape background and SEM stub, imaged at low magnification.
Machining marks and deformation are noted (20 kV, in-column electron detector).
3.3 Bulk piece and computed tomography: Slow‑cooled with connected porosity — The specimen shows
microstructure consistent with cast Al–Si: thin plates and needles of Si embedded in an aluminum
matrix; small particles rich in Fe and Mn; and Mg–Si–Cu precipitates. The spacing and size of these
features (several hundred micrometers), together with the pattern of interconnected pores, indicate
slow cooling—likely in a mold, as in a large sand or permanent‑mold casting. Fast quenching (i.e.,
rapid cooling) produces a much finer microstructure (tens of micrometers) that was not observed.
BRIGHT FIELD DIFFERENTIAL INTERFERENCE CONTRAST
200 𝝻𝝻m
Figure 3. Optical micrographs of the polished bulk section.
Background is aluminum; darker shading shows precipitates.
Synopsis: Analysis of a Aluminum Specimen 4

(a)
CuMg-rich
(b) Matrix (c)
FeMn-rich
Si-rich
Pb-rich
CuFe, MnPb Si MgElectron
(d)
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 compositions in weight percent of the marked
regions in (c): Cu‑rich: 46Al, 22Si, 19Mg, 13Cu. Matrix: 98Al, 2Si, trace Cu. FeMn‑rich: 61Al, 22Fe, 10Si, 6Mn, possible
trace Cu. Si‑rich: 79Si, 21Al. Pb‑rich: 35Al, 33Pb, 13Si, 12O, 6Mg, trace others.
Synopsis: Analysis of a Aluminum Specimen 5

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.
YZ XY
5 mm
Figure 5. Two renderings from the XCT data. The purple surfaces are the pores.
Light blue lines are the approximate location of the sectioning cuts.
Table 2. Microstructure at a glance.
Silicon (Si) These appear as plates or needles in the aluminum matrix. Because silicon improves
precipitates castability, such structures are common features in industrial manufacturing.
Small, bright “Chinese‑script” features common to Al–Si castings, introduced for
Fe/Mn‑rich
improved mechanical properties; their chemistry can shift with trace additions but
intermetallics
their presence is standard.
Cu/Mg‑bearing Typically very fine, these contribute modest strengthening effects—again consistent
precipitates with well‑known alloy families.
Observed in minute amounts as isolated pockets/smears; compatible with trace
Lead‑rich pockets
elements and not indicative of unusual chemistry.
Synopsis: Analysis of a Aluminum Specimen 6

(a) (b)
CuFe, MnPb Si MgElectron
(c)
Figure 6. 15 kV electron beam, bulk sample. (a) Backscatter and (b) False-color X-ray denoting the major phases.
(c) Quantitative X-ray mapping of the major and minor elements.
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. This is consistent with
expected behavior of a typical aluminum casting: it does not radiate on its own.
Synopsis: Analysis of a Aluminum Specimen 7

Figure 7. Gamma
spectroscopy of
metal flakes. Energy
emission (keV)
plotted vs total counts
plotted for one of
the metal flakes.
The spectra show
no emission above
background across
the range of energies.
3.5 Comparison to industry standards — When compared to catalog grades, the sample best matches
A413.1 and 369.1 (with similarities to 361.1/365.1/4032 as well). These eutectics are long-established
aluminum–silicon casting alloys used across automotive, aerospace, and consumer sectors.
Because melts and castings vary by foundry practice, a one‑to‑one element‑by‑element match is
not necessary to assign the alloy family. It is common for castings to deviate slightly from catalog
numbers depending on melt practice, heat treatment, and the location within a large part. The overall
chemistry and microstructure of the sample fall within the expected envelope for these standards.
Table 3. Measured alloy composition compared to important industrial standards. Bold text denotes outside the
standard specification. Broadly speaking, silicon content is most informative of alloy identification and intended
application, so silicon is emphasized in red.
Measured Alloy (reference)
A319.0 319.1 319.2 360.2 361.1 A365.1 369.1 A413.1 4032 4047
ASTM
ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM MIL‑DTL‑
B211/
B969 B179 B179 B179 B179 B179 B179 B179 32495A
B211M
Al 86.099 ± 1.663 Balance Balance Balance Balance Balance Balance Balance Balance Balance Balance
Cr 0.03 ± 0.003 — — — — 0.2‑0.3 — 0.3‑0.4 — 0.1 max —
Cu 0.369 ± 0.019 3‑4 3‑4 3‑4 0.1 max 0.5 max 0.02 max 0.5 max 1 max 0.5‑1.3 0.30 max
Fe 0.97 ± 0.075 1 max 0.8 max 0.6 max 0.7-1.1 0.8 max 0.15‑0.20 1.3 max 1 max 1.0 max 0.80 max
Ga 0.012 ± 0.002 — — — — — — — — — —
Mg 0.298 ± 0.09 0.1 max 0.1 max 0.1 max 0.45‑0.6 0.45‑0.6 0.15-0.60 0.3-0.45 0.1 max 0.8‑1.3 0.10 max
Mn 0.198 ± 0.012 0.5 max 0.5 max 0.1 max 0.1 max 0.25 max 0.3‑0.6 0.35 max 0.35 max — 0.15 max
Ni 0.029 ± 0.003 0.35 max 0.35 max 0.1 max 0.1 max 0.2‑