Title: "Effects of Plastic Deformation on Ultrasonic Additive Manufacturing"

Abstract
Displacing traditional fossil fired energy sources with nuclear energy is critical for providing economic and environmentally sustainable energy, as well as creating international energy independence and security. Current light water reactors provide ~20% of the United States electricity, and advanced reactors designs are under consideration for meeting future energy demand. The production and development of these advanced reactor designs can be exponentially advanced by using additive manufacturing. Ultrasonic Additive Manufacturing (UAM), one of the newest of these methods, is a high strain-rate solid-state bonding technique. The plastic deformation driven bonding allows for complex structures to be created, including embedded optical fiber strain sensors and the bonding of dissimilar and difficult to weld materials. This dissertation investigates several material geometries and industrially relevant engineering alloys to generalize an understanding. Deformation induced point defect vacancies were created during UAM bonding which accelerated interdiffusion of elements, created vacancy clusters, dissolved precipitates, and stabilized a strain induced phase transformation. This dissertation develops an understanding of the fundamental requirements of UAM bonding and the microstructure evolution during plastic deformation.

Bio
Michael Pagan is currently a fifth-year graduate student in Steve Zinkle’s research group. He earned his BS in Materials Science and Engineering at the University of Tennessee, then worked for Alcoa Howmet as a manufacturing process engineer. Upon returning to graduate school, he joined the Nuclear Engineering department and is defending his dissertation this spring semester (April 11th). While in graduate school, Michael was a visiting scholar at the National Institute of Material Science (NIMS) in Japan. His research interests include advanced structural materials, additive manufacturing, severe plastic deformation, and microstructure evolution.