UNIVERSITY PARK, Pa. — When a piece of glass is compromised, the signs of strain can be unmistakable. But understanding that process of deformation before failure in metals is a different matter and a longstanding scientific question that Darren Pagan, the Norris B. McFarlane Faculty Career Development Professorship in the Department of Materials Science and Engineering, hopes to help answer through a Faculty Early Career Development Program (CAREER) Award funded through the U.S. National Science Foundation.
Some of the toughest jobs for metal alloys — such as aviation, power generation and space travel — push these materials close to their limits. During their lifespan, these alloys begin to develop defects before ultimately failing catastrophically.
“Metals are used in the most demanding structural engineering applications and this will only continue,” Pagan said. “As engineers, we’re most interested in what happens when you push these materials close to the point of failure. If we can better understand that process, we can continue to make new alloys and push the boundaries of engineering.”
Pagan said trying to understand why materials fail is as old as the materials themselves. This project aims to look at failure mechanistically and deterministically, rather than statistically.
Using next-generation synchrotron X-ray light sources for this five-year, $626,683 grant, Pagan will lead a team of researchers to investigate how nanoscale defects begin to organize to influence properties such as yield strength, fracture toughness and fatigue life change over the lifespan of the material. Think of bending a paperclip. Do it once, and the metal doesn’t fail, yet the microstructure has changed. Continue to bend, and eventually failure strikes.
Synchrotron X-ray facilities such as the Advanced Photon Source at Illinois’ Argonne National Laboratory allow researchers to use light (X-rays) to look deep inside of materials — at nanoscale resolutions— to spot defects and change.
“Traditional X-ray systems that have been around for over a hundred years and are used all over Penn State equate to the brightness of a candle,” Pagan said. “These advanced synchrotron source equate to the lights at Beaver Stadium, allowing us to see much deeper into these alloys.”
Imagine shining a light through one piece of paper versus a whole stack. A very bright light would be needed to look through the whole stack. Similarly, a very bright X-ray light is needed to look deep through metals. Pagan’s team will travel to these facility partners as part of the grant.
His team also plans to produce guidelines and training to make these advanced X-ray techniques more accessible to research and industry through a partnership with the Air Force Research Laboratory and the John A. Dutton Institute for Teaching and Learning Excellence at Penn State.
Pagan said he hopes this research leads to designing better alloys. He’s working to catalog the defect processes for alloys that can help engineers tweak and tune the microstructure of alloys to better prevent failure.
“This is a case where new technology can answer old questions about how and why metals fail,” Pagan said. “We reached the limit to what we could observe, but advances in technology are allowing us to circle back on these unknowns and push the boundaries of fundamental science even further.”
The NSF awarded this funding under grant number 2539617. This content is solely the responsibility of the authors and does not necessarily represent the views of the funders.