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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//50A OFFIEJIAL ~!! e ..c, The subject of stress-corrosion cracking of metallic glasses, despite its obvious importance for structural applications, has received scant attention in the literature. What little work that has been done has focused on zirconium -based glasses, with the observation that these alloys are very susceptible to stress-corrosion cracking in aqueous environm ents containing chloride ions, likely owing to the fact that they do not form protective oxide surface layers. 22 Mechanical Behavior at Elevated Temperature The discussion above relates to mechanical behavior at temperatures well below the glass transition temperature. At elevated temperatures, the strength drops and plastic deformation transitions to a homogeneous mode, occurring throug hout the specimen instead of being localized into shear bands (Figure 6 ). Above the glass t ransition temperature, the alloy becomes a fluid, with a viscosity that drops exponentially with increasing temperature. Because the strength of the material is low, temperatures either above or below the glass transition may be useful for processing, as discussed above. However, the decrease in strength and the tendency for crystallization at elevated temperatures preclude use of metallic glasses from structural applications at temperatures approaching the glass transition temperature. ::i 1:-' -negl igible fl ow "Ol),'l0. 1 lO" 0.4 0. 0. 0.7 1.2 Trrl/. Figure 6. Deformation Map for Metallic Glasses. As a function of temperature (normalized to the glass transition temperature) and applied shea r stress 1 (norm alized to the shear modulus, μ). At high stresses, plastic deformation occurs inhomogeneously, being localized into shear bands. At high temperatures, plastic deformation becomes homogeneous. The dashed lines represe nt different strai n ra tes. The absolute stresses given are representative of the well-studied bulk metallic glass Zr4 1.2Ti13.8Cu12 .5N i10Be22.5, but the general features of the map are ex pected to apply to all m etallic glasses.23 11 UNCLASSIFIED/ /iiOA OFFI&iIAt 1!18! 8flt I
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