The Motion Mechanism and Thermal Behavior of Sigma 3 Grain Bounda.pdf (34.37 MB)
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The Motion Mechanism and Thermal Behavior of Sigma 3 Grain Boundaries

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posted on 01.09.2016 by Jonathan D. Humberson

Sigma 3 grain boundaries play a large role in the microstructure of fcc materials in general, and particularly so in grain boundary engineered materials. A recent survey of grain boundary properties revealed that many of these grain boundaries possess very large mobilities, and that these mobilities increase at lower temperature, contrary to typical models of thermallyactivated grain boundary motion. Such boundaries would have a tremendous mobility advantage over other boundaries at low temperature, which may explain some observed instances of abnormal grain growth at low temperature. This work explains the boundary structure and motion mechanism that allows for such mobilities, and explores several of the unique factors that must be considered when simulating the motion of these boundaries. The mobilities of a number of boundaries, both thermally-activated and antithermal, were then calculated over a wide temperature range, and several trends were identified that relate boundary crystallography to thermal behavior and mobility. An explanation of the difference in thermal behavior observed in sigma 3 boundaries is proposed based on differences in their dislocation structure.

History

Date

01/09/2016

Degree Type

Dissertation

Department

Materials Science and Engineering

Degree Name

Doctor of Philosophy (PhD)

Advisor(s)

Elizabeth Holm

Exports