Boeing Frontiers
November 2003
Volume 02, Issue 07
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Tech Talk

Boeing puts the pedal to the metal

Imagine a new technology that can not only improve your golf game, but can also help make aircraft smaller, lighter and more durable. Most of us aren't likely to rival Tiger Woods for a PGA crown, but many folks stand to benefit from Boeing's development of structural amorphous metals.

The work that Boeing Phantom Works is doing as part of a three-year, $10 million program funded by the Defense Advanced Research Projects Agency has the potential to be a real game-changer when it comes to metals. And metals are the foundation of much of Boeing's business, whether jet fighter platforms, commercial airplanes or even satellites.

The behavior of conventional metals is limited by their regularly ordered crystal structures. But by using an aluminum alloy whose atomic properties are noncrystalline—with the alloy called "metallic glass"—scientists can manipulate the structure at the most basic level, dramatically improving performance.

"You can create an amorphous material that doesn't even have a crystal structure," said David Bowden, Boeing Technical Fellow and Phantom Works program manager in Advanced Manufacturing Research & Development. "It gives you a lot more freedom to tailor the properties you want. We're trying to use the amorphous state as a pathway to a material structure that you couldn't get within a conventional process and a conventional alloy."

The new metal's first application will be defense-related because DARPA's Structural Amorphous Metals program hopes to boost the lifespan, durability and performance of ground, marine, and air vehicles. But its use surely will transcend the military world.

For this program, Phantom Works has teamed with 17 subcontractors, including seven universities. (In fact, one University of Virginia team member holds a patent on aluminum amorphous alloys.) The schools are doing detailed molecular characterization, using advanced simulation techniques such as molecular dynamics, and studying material behavior, while the program's industrial partners are forging ahead in alloy production.

"We did that so that when the program ended," said Bowden, "we'd have a supply chain" in place.

Bowden said the fruits of the DARPA-Boeing research are five to 10 years away, but companies such as Liquidmetal Technologies are producing products, including "pure energy transfer" golf clubs, from amorphous metals. While their zirconium alloy differs from the aluminum one the Boeing team is developing, the clubs are real-life examples of the process's potential.

"The idea is the metallic glass doesn't absorb the energy of impact," said Bowden, who often totes his amorphous clubs to program briefings as a point of interest. "All the energy stays in the ball, so you hit the ball farther."

Also being studied by the Phantom Works team: calcium-based alloys that have the same crystal structure as aluminum, but with half the density. The team is examining their use for space applications, such as for satellite structural panels currently made from aluminum.

This alloy "weighs a lot less, would cost a lot less, and create extra volume on a spacecraft, which is pretty valuable real estate," said Bowden. "You need all the capacity you can possibly get for the lowest cost."

How it works

Utilizing the discovery that some aluminum alloys can be solidified into an amorphous glassy state, Boeing Phantom Works is working to create an entirely new class of nanostructured aluminum alloys. These lab-produced materials deliver titanium's strength—over a wide temperature range—in a much lighter material.

Metals we use today are crystalline materials, with individual atoms arranged in a regular, ordered structure. But scientists and engineers may soon be able to control these atomic arrangements on a scale currently unattainable by conventional processing methods. That's because of the discovery that some alloys—when solidified from the molten state—form a noncrystalline amorphous material, or metallic glass. With controlled thermal treatments of the glass—a process called devitrification—scientists can manipulate these new alloys to create unique materials with nano-scale microstructural features.

Because high solidification rates are required to form an aluminum glass, the baseline processing approach used is rapid solidification and powder metallurgy. The amorphous powder is then consolidated and processed to yield a nanostructured product.

The Phantom Works team's first-generation aluminum alloys already have registered a tensile strength of 120,000 pounds per square inch, about 25 percent greater than the strength of commercial aluminum alloys. "Having control of the material's structure at the atomic level gives you so much more power to improve properties," said Boeing Technical Fellow David Bowden.

In the future, said Bowden, these aluminum alloys could replace titanium to reduce structural weight, enhance performance, and increase affordability in a variety of aerospace systems.


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