Please consider attending the following: MATERIALS ENGINEERING SEMINAR "Radiation Response of Nanostructured Cu" By Cuncai Fan Purdue MSE Ph.D. Final Exam Advisor: Professor Xinghang Zhang ABSTRACT Irradiation of metals with energetic particles causes severe microstructural damage and degradation of mechanical properties. Prior studies on conventional polycrystalline materials have shown that the radiation tolerance of a material can often be enhanced by introducing a high density of interfaces that act as defect 'sinks' by attracting, absorbing and annihilating radiation induced defects. Nanostructured materials with a large volume fraction of interfaces, therefore, are assumed to be more radiation tolerant than conventional materials. This thesis focuses on understanding the fundamental mechanisms of radiation damage of nanostructured Cu fabricated by magnetron sputtering technique. High-density twin boundaries (TBs) and nanovoids (NVs) were successfully introduced into two distinct nanostructured Cu films with different orientations, including nanovoid-nanotwinned (NV-NT) Cu (111) and nanovoid (NV) Cu (110). The in-situ high-energy Kr ++ (1 MeV) and ex-situ low-energy (< 200 keV) He+ irradiations were subsequently preformed on the nanostructured Cu films. The in-situ TEM studies suggested that TBs and NVs are effective defect sinks that interact with defect clusters and impact their formation and distribution. Meanwhile, the preexisting nanostructures also undergo structural evolution under irradiation, in the form of void shrinkage and spheroidization, and twin boundary migration. In addition, the ex-situ micro-pillar compression tests revealed that the He-irradiated NV-NT Cu contains less defect clusters and maintain good work hardening ability. The underlying mechanisms of radiation-induced void shrinkage, twin boundary migration, and strengthening mechanisms are interpreted based on a combination of TEM analyses and molecular dynamics simulation, and phase-field modeling. This project provides important insight on the design of radiation tolerant nanostructured metals. Date: Wednesday, June 12, 2019 Time: 9:00 A.M. Place: ARMS 1028