Degree

Doctor of Engineering (DEng)

Department

Mechanical & Industrial Engineering

Document Type

Dissertation

Abstract

Despite the significant improvements in manufacturing and synthesis processes of metals and ceramics in the past decades, there are still areas in which the procedure is still frequently more of an art or skill rather than a science. Therefore, systematic and combined experimental and computational studies are required to facilitate the development of techniques that offer thorough understanding of the events taking place during manufacturing and synthesis processes. With regard to these issues, it is paramount to address microscale characterizations and atomic scale understanding of the events during fabrication processes. One of the focuses of this study is unraveling fundamental events and mechanisms during thin film deposition of Cu on TiN substrates. It is demonstrated for the first time that at the very early stage of growth, BCC-Cu grows pseudomorphically on the TiN substrate as a very thin continuous film using a sequential molecular dynamics (MD)/time-stamped force-bias Monte Carlo (tfMC) algorithm. The Nishiyama-Wasserman mechanism, however, causes the Cu thin film to change from predominantly BCC-Cu to predominantly FCC-Cu with abundant nanotwins. As another topic, because of the tendency towards miniaturization in the past decades, studying the mechanical behavior of fabricated specimen at microscale or nanoscale via atomistic simulations is beneficial to characterize the deformation mechanisms associated with the observed phenomena in experiments. In that regard, we examined the impact of geometry and nanotwinned structure on the mechanical response and deformation mechanisms of nanoscale cylindrical Cu pillars capped between rigid substrates under tensile loading at a constant strain rate using MD simulation. The last topic in this dissertation is about the generalized stacking fault energy profile, which is a crucial component of alloy design since it is vital to models of metal plasticity. Models for thermal vibrations must take into account the stacking fault free energy profile; however, existing techniques can only determine how intrinsic stacking faults vary with temperature. We demonstrate how the PAFI linear scaling method, which completely takes into account anharmonic thermal vibrations that can be used to determine the complete stacking fault free energy profile.

Date

2-9-2023

Committee Chair

Moldovan, Dorel

DOI

10.31390/gradschool_dissertations.6050

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