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MATERIALS ENGINEERING
“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