"People accuse me of being highly focused," laughs Professor Wendelin Wright. "I take that as a compliment. I attribute the success of my experiments to how careful I am. I have no tolerance for sloppy data."
For nearly two decades, Wright has dedicated herself to the study of metallic glass, a synthetic material that's stronger than steel and can be injection-molded like a polymer. This trait means precision forming, even on the microscale, can be achieved at lower cost and greater efficiency than manufacturing with conventional metals.
"Naturally occurring metals are crystalline, meaning their atoms are arranged in patterns," Wright explains. "Metallic glass is created by combining molten metals and cooling them at up to a million degrees per second. The resulting material looks like typical metal, but is stronger and has a disordered arrangement of atoms."
It is this lack of order that leads to the one weakness of metallic glass: its brittleness. It resists high stress to a point, but unlike conventional metals that can bend, metallic glasses break abruptly. "The metallic glasses deform through ‘shear banding,' " Wright explains, "a process that lasts just a few thousandths of a second."
Wright and her students study this phenomenon in minute detail. A video camera, recording at 12,000 frames per second, captures the propagation of shear bands. Then, with a flash of light, the material fails completely. "An enormous amount of heat is released when that flash occurs — enough to melt the metal at the fracture surface," says Wright. "People used to believe the temperature spiked before fracture, but our experiments and modeling show that the temperature only rises by a few degrees until the rapid temperature increase due to failure occurs. That was a meaningful contribution."
Wright says having students work with her is one of the most rewarding aspects of teaching at Bucknell. "We work closely, typically for three or four years," she says. "My students learn to use sophisticated equipment, perform experiments to answer open-ended research questions, and often publish their work, similar to what first- and second-year Ph.D. students would do. Research experiences like these build confidence and are a powerful example of the active learning that we seek for all of our students."
The applications for metallic glass include sports equipment, surgical instruments, and electronics casings. "NASA's Jet Propulsion Laboratory is even considering using them to manufacture gears for the Mars Rover and other craft," says Wright. "They truly are the materials of the future."
Posted Sept. 22, 2017