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Title: High Pressure Deformation in Two-Phase Aggregates

Abstract

We investigate the rheological behavior of multi-phase aggregates at high pressure and high temperature. Using synchrotron X-ray radiation as the probing tool, we are able to quantify the stress state of individual phases within the aggregates. This method provides fundamental information in interpreting the behavior of two phase/multi-phase mixtures, which contribute to our understanding of the deformation process at deep earth conditions. We choose MgAl{sub 2}O{sub 4} spinel and MgO periclase as our model materials. Mixtures of various volume proportions were deformed in a multi-anvil high pressure deformation apparatus at pressure of 5 GPa and elevated temperatures. Stress is determined from X-ray diffraction, providing a measure of stress in each individual phase of the mixture in situ during the deformation. Macroscopic strain is determined from X-ray imaging. We compare the steady state strength of various mixtures at 1000 {sup o}C and 800 {sup o}C and at the strain rate in the range of 1.8 to 8.8 x 10{sup -5} s{sup -1}. Our data indicate that the weak phase (MgO) is responsible for most of the accumulated strains while the strong phase (spinel) is supporting most of the stress when the volume proportion is 75% spinel and 25% MgO. The intermediatemore » compositions (40/60) are much weaker than either of the end members, while the grain sizes for the intermediate compositions (submicrons) are much smaller than the end members (5-10 {mu}m). We conclude that a change in flow mechanism resulting from these smaller grains is responsible for the low strength of the intermediate composition mixtures. This study demonstrates an approach of using synchrotron X-rays to study the deformation behaviors of multi-phase aggregates at high pressure and high temperature.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929966
Report Number(s):
BNL-80570-2008-JA
Journal ID: ISSN 0040-1951; TCTOAM; TRN: US0806676
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Tectonophysics; Journal Volume: 439
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; DEFORMATION; GRAIN SIZE; MATERIALS; MIXTURES; PRESSURE RANGE MEGA PA 10-100; RANGE; SPINELS; STRAIN RATE; STRAINS; SYNCHROTRON RADIATION; TEMPERATURE RANGE 0400-1000 K; VOLUME; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Li,L., Addad, A., Weidner, D., Long, H., and Chen, J. High Pressure Deformation in Two-Phase Aggregates. United States: N. p., 2007. Web. doi:10.1016/j.tecto.2007.04.004.
Li,L., Addad, A., Weidner, D., Long, H., & Chen, J. High Pressure Deformation in Two-Phase Aggregates. United States. doi:10.1016/j.tecto.2007.04.004.
Li,L., Addad, A., Weidner, D., Long, H., and Chen, J. Mon . "High Pressure Deformation in Two-Phase Aggregates". United States. doi:10.1016/j.tecto.2007.04.004.
@article{osti_929966,
title = {High Pressure Deformation in Two-Phase Aggregates},
author = {Li,L. and Addad, A. and Weidner, D. and Long, H. and Chen, J.},
abstractNote = {We investigate the rheological behavior of multi-phase aggregates at high pressure and high temperature. Using synchrotron X-ray radiation as the probing tool, we are able to quantify the stress state of individual phases within the aggregates. This method provides fundamental information in interpreting the behavior of two phase/multi-phase mixtures, which contribute to our understanding of the deformation process at deep earth conditions. We choose MgAl{sub 2}O{sub 4} spinel and MgO periclase as our model materials. Mixtures of various volume proportions were deformed in a multi-anvil high pressure deformation apparatus at pressure of 5 GPa and elevated temperatures. Stress is determined from X-ray diffraction, providing a measure of stress in each individual phase of the mixture in situ during the deformation. Macroscopic strain is determined from X-ray imaging. We compare the steady state strength of various mixtures at 1000 {sup o}C and 800 {sup o}C and at the strain rate in the range of 1.8 to 8.8 x 10{sup -5} s{sup -1}. Our data indicate that the weak phase (MgO) is responsible for most of the accumulated strains while the strong phase (spinel) is supporting most of the stress when the volume proportion is 75% spinel and 25% MgO. The intermediate compositions (40/60) are much weaker than either of the end members, while the grain sizes for the intermediate compositions (submicrons) are much smaller than the end members (5-10 {mu}m). We conclude that a change in flow mechanism resulting from these smaller grains is responsible for the low strength of the intermediate composition mixtures. This study demonstrates an approach of using synchrotron X-rays to study the deformation behaviors of multi-phase aggregates at high pressure and high temperature.},
doi = {10.1016/j.tecto.2007.04.004},
journal = {Tectonophysics},
number = ,
volume = 439,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}