Atomistic calculations of rate of long-timescale microstructural evolution

The ability to investigate materials systems at the resolution of individual atoms makes computational simulations a powerful tool for the study of materials phenomena. However, microstructural evolution in complex materials is only meaningfully characterized in laboratory or industry applications by deformation rate and relevant rate coefficients, quantities that require sampling over a timescale too large for traditional atomistic methods to probe. New methods and techniques have to be developed in order to obtain useful information of rate from atomistic simulations. In this thesis, we explore a set of four problems, related to two long-timescale microstructural phenomena, creep and oxidation, and use a variety of atomistic methods appropriate to each problem to demonstrate the techniques of obtaining rate information. Creep due to vacancy-driven dislocation climb critically depends on the movement of the vacancies in the bulk towards dislocation cores, and for the first contribution of the thesis we investigate the influence of carbon solute atoms on vacancy diffusion pathways in bulk BCC Fe. Using these results, we draw explanations of the trends of the experimentally-observed rate of creep. It is well-known that vacancy energetics vary with distance from dislocation cores due to the dislocation strain field, but the effect this has on creep by the dislocation climb mechanism is not well understood. In the second contribution of the thesis, we present an investigation of the vacancy-dislocation interaction of BCC Fe.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Materials Science and Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Lau, Timothy Tin-Ming, 1984-

Advisor dc:contributor.advisor

• Sidney Yip.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/53242

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/53242