ABSTRACT
As an aid to understanding the high-temperature microstructures of
rocks, the development of microstructures in the hexagonal organic
material, octachloropropane, was studied with in-situ optical
microscopy. It was found that the deformation behavior of grains
in hard and soft orientations for slip is different during simple
shearing, although they both grow. Strain heterogeneity is induced
by partitioning of deformation into relatively increased
components of rigid-body rotation and translation in hard grains
and strains in soft grains.
A steady-state foliation, having a constant intensity and
orientation was observed in simple shearing. The steady state is
maintained by a balance between foliation-strengthening and
-weakening processes. The major foliation-strengthening process is
intragranular strain, and the major foliation-weakening process is
dynamic recrystallization including migration of straight or
slightly wavy grain boundaries, grain dissection and rotational
recrystallization. Other minor weakening processes are grain
amalgamation, relative rigidity of hard grains and grain boundary
sliding. Foliation intensity is lower than the axial ratio of the
bulk strain ellipse by a factor 0.2 - 0.4 at a total shear strain
of 1.3 - 1.8, indicating that grain-shape foliations of this type
cannot be used for strain calculation.
Subgrain boundaries which appear similar under optical microscopy
originate in seven different ways. They are classical
polygonization, kinking, misorientation reduction, grain
coalescence, impingement of migrating subgrain boundaries,
edgewise propagation, and static development of subgrain
boundaries from optically strain-free grains. The preferred
orientation of subgrain boundaries with respect to the grain-shape
foliation is symmetric in pure-sheared samples and asymmetric in
simple-sheared samples.
Grain boundary sliding can occur by discontinuities in the strain,
rotation and/or translation components of deformation across the
boundary in deforming samples. Grain boundary diffusion and
intragranular plastic deformation are found to be effective in
accommodating grain boundary sliding. Grain boundary openings can
develop in association with grain boundary sliding, preferentially
along grain boundaries at a low angle to the shortening direction.
Once grain boundary openings occur, they continuously change their
shape and are eventually closed by thrusting of sliding grains and
grain overgrowth into the openings. An approximately equal volume
of new openings grow in other places, however, maintaining a
steady ratio of 0.5-3% of the sample volume without development of
any large scale fracture. The opening and closing of grain
boundaries usually involve neighbor switching of surrounding
grains.
Ree, J-H., 1991. High temperature deformation of
octachloropropane: a microstructural study.
Unpublished PhD dissertation, State University of New York at
Albany. 216pp., +xiii
University at Albany Science Library call number: SCIENCE
MIC Film QE 40 Z899 1991 R443
Copies of this PhD dissertation can be ordered
from Proquest UMI
Front matter (title,
table of contents, abstract, acknowledgements) - 0.4MB pdf
file
Photo pages in dissertation
(greyscale
photos with captions): - 4.8MB pdf file
Return to PhD dissertations completed
in the Geological Sciences Program, University at Albany