WPI Research is the research magazine of Worcester Polytechnic Institute. It contains news and features about graduate research in the arts and sciences, business, and engineering, along with notes about new grants, books, and faculty achievements.
Issue link: http://wpiresearch.epubxp.com/i/90696
VIDEO EXTRA Professor Sisson on the need for designer metals. Right, Richard Sisson and graduate student Danielle Belsito examine a metal sample under a light microscope. When viewed under the scanning electron microscope in Washburn, more of the sample's microstructure is revealed, as seen in this image of a cold-sprayed aluminum powder. Super-Materials by Design "Metallurgists heat things up and cool things down," Sisson says. "The key is how hot, how long, and how long you cool it in the end," adding that all of those factors affect the nanoscale microstructures inside the alloys, and thus their physical properties. Armed with a $4 million contract from the U.S. Army, Sisson and his colleagues are using computer models to predict the response of metal alloys to heat treatments, with the goal of developing computational tools that can be used to refine existing aluminum alloys and develop new ones that the service can use to build and repair its airplanes and ground vehicles. The alloys the Army now uses are strong, but not particularly tough or ductile. Typically, they are first turned into powder and then sprayed at high temperatures. Everything from the initial composition of the powders, to the way they are heated, influences their performance. One of Sisson's goals, therefore, is to develop processing tech- niques that can enhance toughness and ductility without sacrificing strength. Another is to invent new alloys strong enough to be used structurally, tough enough to function as armor, and light enough to improve the mobility and gas mileage of army vehicles such as Humvees. "They want super- materials," Sisson says. "They want them to have three or four functions at once." That's a tall order. But Sisson has more than a few tricks up his sleeve. For example, the databases that he uses to power his computer models often lack crucial data on the physical properties of specific alloys. So Sisson is conducting physical experiments to fill in those lacunae, improving his ability to accurately simulate each step in the creation, treatment, and application of a given metal. Ultimately, that will help him design new and better materials — a task that depends on understanding exactly what properties are required, and which processes will produce the microstructures needed to generate them. Sisson is also investigating a low-temperature method of applying the alloys, known as cold spraying, that accel- erates the powders to supersonic speeds without actually melting them. Though well-suited to preparing vehicle parts at relatively low cost, the process is still in the experimental stages. Sisson acknowledges that developing next-generation alloys using next-generation technologies is no small undertaking. But the wizard of Washburn is undeterred. "If it was easy," he says, "everyone would be doing it." VIDEO EXTRA [12] Professor Wang on how to make a better flow battery. wpi.edu/+research