Dynamic grain boundary migration and fabric development: observations, experiments and simulations
Mark Walter Jessell 1986
A Dissertation submitted to the State University of New York at Albany in partial fulfillment of the requirements for the degree of Doctor of Philosophy
College of Sciences and Mathematics, Department of Geological Sciences
Advisor: W.D. Means

In-situ observations of a deforming aggregate of the hexagonal material octachloropropane have been analysed. Calculations of micro-strains and measurement of c-axis orientations have enabled the processes influencing fabric development to be distinguished, and the importance of dynamic grain boundary migration to be assessed. It was found that in this material, inter-grain strain contrasts could be significant, and that the effect of grain boundary migration was to modify the fabric in a measurable way. A simple model for the driving force for grain boundary migration based on dislocation density contrasts, as controlled by intra-grain strains and grain orientations, is proposed and tested and can account for the migration direction of most of the observed boundaries.
Several grain-scale microstructures are described that demonstrate the migration direction of once-mobile grain boundaries in a naturally deformed quartzite. I present an analysis of the sense of migration of the boundaries and the characteristics of the patterns of relative grain growth and shrinkage. Grain boundary migration can be correlated with the relative crystallographic orientations of neighbouring grains.
A new computer simulation of the development of grain shape and crystallographic preferred orientations is presented. This model combines homogeneous strains, simplified versions of the lattice rotations predicted by Taylor-Bishop-Hill theory, mobile grain boundaries and the nucleation of new grains, and allows the progressive development of the fabrics to be followed. The model generates several commonly measured quartz c-axis fabrics, while at the same time predicting characteristic variations in average grain sizes and the intensity of grain shape fabrics that arise from differing recrystallization regimes and strain geometries.

Jessell, M.W., 1986. Dynamic grain boundary migration and fabric development: observations, experiments and simulations. Unpublished PhD dissertation, State University of New York at Albany. 270pp., +xv
University at Albany Science Library call number:  SCIENCE MIC Film QE  40 Z899 1986 J48
Copies of this PhD dissertation can be ordered from Proquest UMI

        Front matter (title, table of contents, abstract, acknowledgements) - 0.3MB pdf file
        Photo pages in dissertation (colour and greyscale photos with captions): - 6.4MB pdf file

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