Multimillion-dollar award from U.S. Army to fund advanced manufacturing research
Associate Professor Hang Yu is leading a team investigating how solid-state manufacturing approaches can help create and repair metal in wartime and beyond.
Metal is always in high demand for the U.S. military, which uses an estimated 750 million tons annually for everything from repairing a corroded battleship or building a new armored tank. But traditional metal manufacturing that relies on casting or forging components can be slow, costly, and ineffective.
To find better approaches, the U.S. Army Research Laboratory is investing potentially millions of dollars over five years, through a cooperative agreement, in the cutting-edge advanced manufacturing research of a group of faculty led by Hang Yu, associate professor of materials science and engineering.
Other collaborators include:
- Christopher Williams, the L.S. Randolph Professor of Mechanical Engineering
- Zhenyu "James" Kong, the Ralph H. Bogle Professor of Industrial and Systems Engineering
- David Higdon, professor of statistics
- Mitsuhiro Murayama, professor of materials science and engineering
How to 3D-print metal
Central to Yu’s research is a 3D-printing process called additive friction stir deposition (AFSD), which uses friction to reshape high-strength metals like aluminum, steel, and titanium.
Picture rubbing a chunk of Play-Doh between your hands to soften and shape it. AFSD similarly softens a metal stick called a feed rod by pushing it through a spinning tool until friction makes it pliable enough to shape. The plasticized metal is then extruded like toothpaste and spread in layers.
“You can deform material quickly because the stirring itself heats up and softens the material. Then you can deposit it at a very high rate on a large scale,” Yu said. “In additive friction stir deposition, the thermal and mechanical go together. That’s why it’s so efficient.”
Because the metal never fully melts, it’s less prone to defects such as cracking and porosity. Indeed, the friction process has been shown to purify and improve the properties of metal by changing its underlying microstructure, making AFSD a good candidate for upcycling low-quality scrap metal — one of the research avenues Yu’s team will explore.
“The Army has a lot of interest in how you efficiently make use of battlefield steel scrap,” said Yu, the author of a popular textbook "Additive Friction Stir Deposition." “There would be cost savings and potential benefits to the environment and the supply chain.”
While Yu originally used an AFSD machine produced by Blacksburg-based industry partner MELD, his team has created a smaller, portable version that could make on-site repairs of damaged military equipment.
Long-term impact of advanced manufacturing
Beyond defense, AFSD and other advanced manufacturing approaches could have broad applications, including for the auto industry. “Federal research funding is critical to enabling us to advance future manufacturing technologies and the future manufacturing workforce, all of which will be translated to commercial products to improve their performance and our everday experiences,” said Williams, a leader in advanced manufacturing at Virginia Tech and one of the project's co-investigators.
Thinking bigger, Yu said AFSD could be an effective way to manufacture metal in space. While traditional metal manufacturing would be hampered by different gravities and environmental impurities on the moon or on Mars, “ASFD is more robust, and you can deploy it in some austere conditions.”
The other collaborators, Yu said, study similar advanced manufacturing technologies or contributing expertise in AI, machine learning, and statistics that will accelerate the research process. “I think that's the future for advanced manufacturing materials,” he said. “You need an interdisciplinary team to do this work.”
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