Scientists at the University of Pittsburgh are the recipients of a grant from the National Science Foundation to study the formation of microstructures in aluminium alloys as they solidify through a unique transmission electron microscope developed at the Lawrence Livermore National Laboratory.
The university’s proposal, entitled “In-situ transmission electron microscopy of microstructure formation during laser irradiation induced irreversible transformations in metals and alloys,” won the three-year, US$500,000 grant from the NSF Division of Materials Research. Pitt’s investigative team is headed by Jörg M.K. Wiezorek, Ph.D.
The grant allows the Pitt researchers to access the dynamic transmission electron microscope (DTEM) at Lawrence Livermore National Laboratory. The DTEM is capable of recording nano-scale changes over the period of nanoseconds, which is a capability no other electron microscopes in existence have. The researchers will use this technology to study rapid solidification processes that occur when aluminium alloys harden after being melted by a laser or electron beam techniques, similar to those processes used in welding, joining, and additive manufacturing.
“Predicting microstructure formation during rapid non-equilibrium processing of engineering materials is a fundamental challenge of materials science. Prior to advent of the DTEM we could only simulate these transformations on a computer,” said Wiezorek. “We hope to discover the mechanisms of how alloy microstructures evolve during solidification after laser melting by direct and locally resolved observation. Thermodynamics provides for the limiting constraints for the transformations of the materials, but it cannot a-priori predict the pathways the microstructures take as they transition from the liquid to the final solid state.”
He went on to say that the data will help validate computer models and identify how changes in composition and temperature change the microstructure.
“We are hoping to unravel details of the kinetic pathways taken from the liquid to the final solid structure,” Wiezorek said. “This research will help us to refine solidification related manufacturing processes and to identify strategies to optimize how materials perform.”