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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//FOR err1e1J1tt t,91! 014[1 Metallic Glasses: Status and Prospects for Aerospace Applications Summary Metallic glasses combine some of the advantageous mechanical properties of metals-strength, stiffness, and in some cases toughness-with the processing flexibility usually associated with thermoplastic polymers. The absence of crystalline defects allows metallic glasses to be much stronger than conventional alloys but also means they have near-zero tensile ductility and poor fatigue resistance. In structural applications, therefore, metallic glasses are most likely to be useful in the form of composites consisting of ductile crystalline dendrites in a metallic glass matrix. These dendritic composites sacrifice some strength but can have exceptionally high fracture toughness, as well as good fatigue resistance, and could replace high-strength steels in certain load-limited structural components in aerospace vehicles where space is limited. Because they are true glasses, thermoplastic forming near the glass transition temperature affords metallic glasses tremendous flexibility in processi'ng. For instance, metallic glass components can be formed in a single step (for example, by injection molding) in complex geometries that would be difficult or impossible to produce with conventional alloys. In addition, metallic glass foams can be made with relative ease, raising the possibility of making structural foams with high strength and stiffness. Finally, because they lack a crystalline grain structure, metallic glasses can be used to form nanoscale features with high fide ity. This may make metallic glasses useful in a variety of micro-electromechanical systems (MEMS) applications. Metallic glasses also have significant limitations for aerospace applications, however. Foremost among these is a lack of good glass-forming alloys; in particular, there are no good aluminum-rich glass-forming alloys, the known titanium-based alloys are either relatively dense (owing to high concentrations of alloying elements) or contain beryllium, and the known magnesium- and iron-based alloys are all quite brittle, with low fracture toughness. Although metallic glass matrix composites can have outstanding properties (particularly strength and fracture toughness), the number of good composite systems known at present is also quite limited. Therefore, in order for metallic glasses (and their composites) to be of broad utility in aerospace structural applications, progress in the following areas is required: • Development of new lightweight alloys and composite systems, preferably by computational and/or combinatorial approaches rather than by trial and error. • Understanding of mechanical behavior, especially: V UNCLASSIFIED/ /liiAR AfifilCIAk lel&E 8,.L'&'
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