Date of Graduation

5-2013

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor

Spearot, Douglas E.

Reader

Zou, Min

Abstract

Polycrystalline metallic materials commonly exhibit the Hall-Petch relationship, which states that decreased grain size leads to increased strength. As a result, nanocrystalline metals, which are defined as polycrystalline metals with average grain diameters on the nanoscale, exhibit ultra-high strength phenomenon. Despite their incredible strength, the applications of these materials are severely limited due to thermodynamic instability that causes low temperature grain growth and a reduction in the enhanced properties. It is known that dopant atoms located at the grain boundaries in nanocrystalline metals can reduce this effect and stabilize the microstructure of these materials, but little is known about the impact they have on dislocation nucleation from the grain boundaries. The goal of this research is to study the effects that antimony atoms segregated to the grain boundaries in nanocrystalline copper have on strength during nanoindentation via molecular dynamics (MD) simulations. In nanocrystalline Cu-Sb alloys, with low concentrations of Sb segregated to the grain boundaries, the microstructure is stabilized, without any significant effect on strength during nanoindentation. In pure nanocrystalline Cu, the location of the indentation has a significant effect on the response of the sample.

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