HR: 1330h
AN: V42A-0322    [PDF]
TI: X-ray Stress Analysis in Deforming Materials: Models and Observations
AU: * Li, L
EM: lilli@notes.cc.sunysb.edu
AF: Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794 United States
AU: Weidner, D J
AF: Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794 United States
AU: Durham, W
AF: Lawrence Livermore Laboratory, University of California, Lawrence Livermore Laboratory, PO Box 808, Livermore, CA 94550 United States
AU: Chen, J
AF: Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794 United States
AU: Mei, S
AF: Lawrence Livermore Laboratory, University of California, Lawrence Livermore Laboratory, PO Box 808, Livermore, CA 94550 United States
AU: Davis, M
AF: Mineral Physics Institute, State University of New York at Stony Brook, Stony Brook, NY 11794 United States
AB: The relationship between the stress field and strain field in a polycrystalline system that is undergoing deformation has been the focus of many materials science studies since the late 1920's. The Taylor and Sachs models assume that the plastic process is enabled by dislocation flow on specific lattice planes and specific Burger's vectors. Then the relationship between stress and strain is controlled by the orientation of an individual grain with respect to the stress field, von Mises criteria, and the critical resolved stress on the dislocation that is necessary for flow. We use the Taylor model, the Sachs model and a self-consistent model to predict the flow-stress during plastic deformation of polycrystalline MgO with slip system of (110)(1-10), (111)(1-10), (100)(011) at different critical resolved shear stress ratios (CRSS) on the different dislocations. The prediction of the models is correlated with the results of X-ray diffraction measurements. Uniaxial deformation experiments on polycrystalline and single crystalline MgO (periclase) samples were conducted in situ using white X-ray diffraction with a multi-element detector and multi-anvil high-pressure apparatus at pressure up to 6 GPa and temperature up to 1300 K. A deformation DIA (DDIA) was used to generate pressure and control a constant compression speed. Elastic strains and plastic strains were monitored using X-ray diffraction spectra and X-ray imaging technique respectively. The correlation of the data and models suggests that Taylor and Sachs model should represent the extreme upper- and lower- bound for the polycrystal models with the presence of plasticity, while the Reuss and Voigt models are appropriate for the elastic region of deformation, before the onset of plastic deformation. The similarity of elastic strains among different lattice plane suggests that {110} slip systems is marginally the most significant slip systems in MgO at high pressure at high temperature with the selected critical resolved shear stress ratio less than 2.
DE: 3902 Creep and deformation
DE: 3904 Defects
DE: 3924 High-pressure behavior
DE: 3994 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting