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Designing Better Aluminum Alloys

On November 2, 1944, Howard Hughes’s infamous plane the Spruce Goose made its inaugural and final flight, traveling a single mile. Contrary to its name, the Spruce Goose was constructed primarily of laminated birch in an attempt to work within the government’s wartime materials restrictions. Weighing approximately 300,000 pounds, the plane was estimated to travel less than a quarter of a mile per gallon of fuel. In contrast, a modern Boeing 747 travels approximately five miles on a gallon.

Aside from the modern technology operating within the 747, the most obvious difference between the two aircraft lies in their construction materials. The 747 is made of a high-tech aluminum alloy. The study and improvement of aluminum alloys continue to make up an important area of research within the field of materials science.

Lighter, more heat-resistant alloys can improve the performance and fuel efficiency of transportation vehicles like cars and planes. This is precisely the subject Seungha Shin, assistant professor of mechanical, aerospace, and biomedical engineering, proposes to address with his JDRD project. Shin’s team, in conjunction with his partner Amit Shyam, a research scientist at ORNL, is investigating mass and thermal transport near microstructural interfaces in the search for better-designed aluminum alloys.

 

“Aluminum is kind of a soft metal, so in order to have better mechanical properties we add copper. In mechanical properties, most failures occur near the interface, so when designing a microstructure, the interface is very important,” said Shin.

Shin hopes his project will lead to a more thorough understanding of how to design alloys to create microstructures that provide specific effects, such as greater durability under high temperature conditions.

“Normally, light metals are not that good at high temperatures, so to use that kind of lightweight metal we need to develop some new materials,” said Shin.

Microstructures have an important role to play in the development of these new materials. The unique microstructure of a material determines its physical properties, such as toughness, corrosion resistance, and thermal transport behavior. These properties then determine the applications and industries for which that material is suited. Essentially, microstructures dictate the uses of materials.

“If we have an aluminum-copper alloy, it creates a certain phase of microstructure called the theta phase. It begins all mixed together, then forms the theta prime phase followed by the theta phase,” said Shin. “The theta phase is not good, but the theta prime phase can create a stronger aluminum alloy. We want to prevent the diffusion, or transition, from the theta prime to theta phase.”

Shin’s team will focus on computational simulations of interfacial transport at the atomic level with the goal of developing a theoretical framework for controlling these properties. His ORNL partners will model on both fundamental and system scales. Shin’s work will provide the missing piece for effective alloy design, with wide-ranging applications in air and ground transportation.

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