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This Defense Intelligence Reference Document, dated 14 December 2009, was prepared by the Defense Intelligence Agency's Defense Warning Office under its Advanced Aerospace Weapon System Applications program. It is a technical review of metallic glasses that covers their structure, processing, mechanical behavior and possible aerospace uses. It concludes that composites with ductile dendrites in a glass matrix hold the most promise for structural use. It also finds that widespread aerospace adoption depends on developing new lightweight glass-forming alloys.
From the source: Release of 2026-09-18 Incident: 12/14/09, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys metallic glasses as a potentially important class of aerospace materials and describes their amorphous structure as offering very high strength and unusual manufacturing advantages, but also significant drawbacks, especially poor ductility and fatigue resistance. The document concludes that the most promising aerospace applications are likely to come from metallic-glass-matrix composites rather than single-phase glasses, because these composites can retain high strength while greatly improving fracture toughness and fatigue performance, potentially enough to substitute for high-strength steels in some space-limited structural uses. At the same time, the report judges that broader aerospace use will depend on substantial progress over the next 20–50 years in alloy design, processing, and especially the development of lightweight systems, including aluminum-based options.
UNCLASSIFIED//fOK OfflEIAL ~SE 8PtLY Other Properties: Magnetic, Electrical, Optical, Thermal, and Acoustic Although most of the current interest in metallic glasses centers on their mechanical properties, it is appropriate to consider other properties of potential utility. Of these, the magnetic properties of ferromagnetic metallic glasses stand out. 24 A variety of ferromagnetic glass-forming alloys exist, mostly based on transition metals (iron, nickel, and cobalt). The presence of alloying elements (necessary to make the material glass-forming) means the saturation magnetization of metallic glasses is not as large as that of the pure elements. However, some amorphous alloys have very low coercivity (a measure of how strong a magnetic field must be to change the direction of magnetization of the material) owing to the lack of crystalline defects (such as grain boundaries) and magnetocrystalline anisotropy. In addition, the relatively high electrical resistivity of amorphous alloys (see below) minimizes eddy current losses caused by high -frequency magnetization/demagnetization. Some amorphous alloys also have strong magnetoelastic effects (coupling between magnetic properties such as susceptibility or magnetization and elastic strain). Current and potential future applications of these magnetic properties are discussed below. Like crystalline alloys, metallic glasses have conduction electrons that make them both electrically and thermally conductive,25 although their structural disorder and high alloy content make them poor conductors. In addition, in a behavior that is useful in some applications, the conductivity of metallic glasses is not very sensitive to temperature; an exception is near absolute zero, where some amorphous alloys become superconducting. Another consequence of tlhe amorphous structure of metallic glasses is that they tend to have very low acoustic damping. This may be useful in applications such as vibrating structure gyroscopes for vehicle orientation. 26 A common misperception among those hearing about metallic glasses for the first time is to think they are transparent. This is not the case; amorphous alloys are highly reflective, with a shiny luster similar to that of other metals (Figure 7). This is a result of the presence of the conduction electrons, which scatter and absorb incident light. 12 UNCLASSIFIED/ /EAR O551£1.t.k W&li 8PtLY
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