Microstructural study of two-phase marbles in simple shear

Microstructural and textural observations have been conducted on synthetic calcite with 20 wt% quartz deformed in simple shear using transmission electron microscopy and selected-area diffraction. The marbles were deformed at 873, 973, and 1073 K at a stress of 305, 222, and 127 MPa, respectively, and a strain rate of 10 -4 s -1. The microstructure, shape-preferred orientation (SPO), grain aspect ratios, lattice-preferred orientation (LPO), dislocation densities, and grain sizes were compared to the results of other studies on similar carbonates deformed in triaxial loading, torsion, and simple shear. Microstructures are consistent with other marbles at similar temperatures and stresses, with the only major difference in grain size. The SPO and aspect ratios differ from the theoretical calculations, but are consistent with other marbles. This SPO and aspect ratio is consistent with grains behaving as high-viscosity particles with low-viscosity boundaries. Loading conditions appear to affect the strain at which recrystallization starts, with evidence for new grains at a strain of 3 in this study, compared to minimum strains of at least 4 for others. Dislocation densities are 3.5 x 10 13 m -2 , 8 x 10 13 m -2, and 1.3 x 1014 m -2 for the samples at 873, 973, and 1073 K, respectively, and when inserted into a paleopiezometer, the predicted stresses are 347, 257, and 156 MPa, respectively, which is in good agreement with the applied conditions.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Zucker, Rachel V. (Rachel Victoria)

Advisor dc:contributor.advisor

• J. Brian Evans and Samuel M. Allen.

• 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/1721.1/58189

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/58189