ORNL Synopsis: Analysis of an Aluminum Specimen

Synopsis: Analysis of a Aluminum Specimen3
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
sample is an aluminum–silicon (Al‑Si) alloy near the Al–Si
eutectic. The dominant elements are aluminum (~86 wt%)
and silicon (~12 wt%), followed by iron (Fe, ~1 wt%),
copper (Cu, ~0.37 wt%), magnesium (Mg, ~0.30 wt%),
zinc (Zn, ~0.20 wt%), and manganese (Mn, ~0.20 wt%).
Several other elements (lead [Pb], chromium [Cr], nickel
[Ni], titanium [Ti], and gallium [Ga]) appear only at trace
levels (tens to hundreds of parts per million). These are
the expected elements within common casting grades and
do not suggest exotic additives. The shavings and the bulk
sample had identical chemistry for all elements measured,
by multiple techniques, within the analytical uncertainties
of the instruments. This chemical composition is consistent
with a near‑eutectic Al–Si casting alloy—conventionally
used when designing molten aluminum to flow easily into a
mold and reproduce fine details.
3.2 Shavings vs. cross‑sectioned shavings: Impact of drilling
changes — The shavings given to ORNL show folding
tool marks from drilling performed before AARO acquired
the material. The undisturbed interior was exposed by
embedding the sample in epoxy, cross‑sectioning, and
polishing. In the interior, ORNL observed a suite of phases
consistent with standard cast Al–Si alloys: aluminum
Table 1. Bulk composition summary
(weight %). Values are rounded; trace
elements shown for context. Analyses
of the bulk sample and shavings were
compositionally consistent.
Instrument Element wt%
GD‑MS Al 86.10
GD‑MS Si 11.90
ICP‑OES Fe 0.97
ICP‑OES Cu 0.37
ICP‑OES Mg 0.30
ICP‑OES Zn 0.20
ICP‑OES Mn 0.20
ICP‑MS Pb 0.04
ICP‑MS Cr 0.03
ICP‑MS Ni 0.03
ICP‑OES Ti 0.03
ICP‑MS Ga 0.01