Pitt engineers will use Lab's electron microscope to study rapid metal solidification

University of Pittsburgh engineers will utilize a unique transmission electron microscope developed and housed at Lawrence Livermore National Laboratory (LLNL) to better understand how microstructures form in metals and alloys as they solidify after laser beam melting.

Under a three-year, $500,000 grant from the National Science Foundation, Jörg Wiezorek, a professor of mechanical engineering and materials science at Pitt, and his team will use the Lab’s dynamic transmission electron microscope (DTEM) to study the rapid solidification of aluminum alloys associated with laser or electron beam processing technologies, including welding, joining and additive manufacturing.

Unlike a traditional transmission electron microscope, DTEM uses lasers to achieve high time resolution, allowing it to record nano-sized transformations in materials on a time scale of nanoseconds to microseconds.

"DTEM allows you to see the interface between the solid and liquid during rapid solidification, which is extremely hard to do," said Joe McKeown, an LLNL materials scientist who works with the microscope and collaborates with Wiezorek. "We can image this process as it’s moving rapidly, and from that we can measure just how fast it’s going. There’s no other technique to do that."

McKeown said the data collected from the study could improve predictive capabilities for metal additive manufacturing and validate existing computer models.

"We want to develop models across a broad range of velocities," McKeown said. "If we didn’t have this technology, you could run these rapid solidification experiments but you wouldn’t know the pathway from point A to point B."

Pitt will begin sending students to the Lab later this fall. Wiezorek called predicting the microstructure formation during processing a "fundamental challenge of materials science." The study, he said, hopefully will uncover details of the pathways the materials take from a liquid to a solid, and identify strategies to optimize how they perform.

"Prior to the advent of the DTEM we could only simulate these transformations on a computer," Wiezorek said in a news release. "We hope to discover the mechanisms of how alloy microstructures evolve during solidification after laser melting by direct and locally resolved observation."

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