DIRD-01: Metallic Glasses for Aerospace

Brief

DIRD_01 is the first of 38 Defense Intelligence Reference Documents produced in FY 2009 for the Advanced Aerospace Weapon System Applications (AAWSA) Program, which operated under DIA sponsorship and was linked to Senator Harry Reid's AATIP initiative. The document surveys amorphous metal alloys, metallic glasses, across structure, processing, and mechanical behavior, concluding that their exceptional strength (iron-based alloys reaching approximately 4 GPa, two to three times conventional high-strength steels) is offset by near-zero tensile ductility and an absence of good lightweight glass-forming alloys in aluminum and magnesium systems. Dendritic composites, ductile crystalline phases embedded in a metallic glass matrix, are identified as the most viable near-term structural application. The author projects 20-50 years of continued research before widespread aerospace adoption is feasible, contingent on the development of new lightweight alloy systems.

Metadata

Agency

Defense Intelligence Agency (DIA)

Release

2022-03-25

Type

PDF • .pdf

Length

30 pages

Classification

UNCLASSIFIED//FOR OFFICIAL USE ONLY

Programs

Advanced Aerospace Weapon System Applications (AAWSA) Program, AATIP

Tags

AAWSAP, AATIP, exotic materials, metallic glasses, amorphous alloys, aerospace structures, DIA DIRD, advanced propulsion materials

Key points

• Document is product one in an FY 2009 series of advanced technology reports produced under DIA's Advanced Aerospace Weapon System Applications (AAWSA) Program; author and producing office are redacted under 10 USC 424 and b(6).p.2
• Metallic glasses achieve yield strengths 2-3x those of crystalline alloys of similar composition because their amorphous structure precludes the existence of dislocations, the primary mechanism of plastic deformation in conventional metals.p.12
• Best iron-based metallic glass alloys reach approximately 4 GPa, two or three times greater than conventional high-strength steels.p.12
• No good aluminum-rich glass-forming alloys exist; known titanium-based alloys are either dense due to high alloying element concentrations or contain beryllium; magnesium- and iron-based alloys are brittle with low fracture toughness.p.5
• Dendritic composites (ductile crystalline dendrites in a metallic glass matrix) sacrifice some strength but achieve exceptionally high fracture toughness and good fatigue resistance, making them candidates to replace high-strength steels in load-limited aerospace components.p.5
• Thermoplastic forming near the glass transition temperature enables complex geometries, including injection-molded net-shape parts and blow-molded thin-walled structures, that are difficult or impossible with conventional alloys.p.5
• Early metallic glasses (1960s-1970s) required critical cooling rates of 10^4 to 10^7 K/s, limiting maximum thickness to under 100 μm; multi-component alloy research has since reduced critical cooling rates to 0.1 K/s or lower, enabling bulk castings exceeding 1 cm.p.9
• Glass-forming ability cannot be predicted computationally from first principles; alloy identification remains largely trial and error, and only a limited number of alloys can be cast to a 1-cm section thickness.p.9
• Table 1 lists eight bulk glass-forming alloys with maximum casting thicknesses from 10 mm to 72 mm; the Pd40Cu30Ni10P20 system holds the record at 72 mm.p.9
• Author projects that continued work over the next 20-50 years is highly likely to yield significant advances, but widespread aerospace adoption depends critically on new lightweight alloy development.p.6

Verbatim

• 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.

  p.5

• 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.

  p.5

• It is highly likely that continued work over the next 20-50 years will result in significant advances in all these areas, and that metallic glasses and metallic glass matrix composites will see increasing acceptance as structural materials.

  p.6

• Whether or not they achieve widespread use in aerospace applications, however, depends critically on the development of new, lightweight alloys.

  p.6

• At present, it is not possible to predict a priori the glass-forming ability of an alloy of arbitrary composition.

  p.9

• Glass formation and crystallization are therefore competitive processes; which one will occur depends on the material and the processing conditions.

  p.8

• the best iron-based alloys have a strength of approximately 4 GPa-again, two or three times greater than those of conventional high-strength steels.

  p.12

Most interesting

• This document contains no direct reference to UAP, recovered craft, or non-human technology. Its inclusion in the AAWSAP DIRD series implies the program treated exotic materials science as relevant to understanding advanced aerospace vehicles of unknown origin.
• The Pd40Cu30Ni10P20 alloy, already a known bulk metallic glass in open literature, holds the record casting thickness in Table 1 at 72 mm, a fact cited from open academic sources, suggesting the DIRD drew primarily from unclassified research.
• Blow-molding of metallic glasses into thin-walled bottles is demonstrated in Figure 3, crediting Professor Jan Schroers at Yale University, indicating the DIA was tracking university-level materials research for potential aerospace relevance.
• Metallic glasses can be nanoimprinted with high fidelity due to their lack of crystalline grain structure, making them candidates for MEMS devices at scales conventional metals cannot achieve.
• Early metallic glass ribbons were discovered in the 1960s-1970s; the FY 2009 DIRD represents the U.S. intelligence community's formal assessment of whether five decades of subsequent research had matured the technology to aerospace utility.
• The document is dated 14 December 2009 with an Intelligence Community Original Document (ICOD) date of 1 December 2009, a 13-day gap suggesting rapid production turnaround for the program sponsor.
• Beryllium content in known titanium-based glass-forming alloys is flagged as a practical obstacle, since beryllium is a controlled, toxic material that complicates industrial manufacturing and handling.