Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session Q3: High Pressure Strength II |
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Chair: Guoyin Shen, HPCAT/CIW Room: Renaissance Ballroom AB |
Wednesday, June 29, 2011 4:00PM - 4:30PM |
Q3.00001: Plasticity under pressure: static experiments and models Invited Speaker: Over the last few years, we developed new methods for the study of plastic properties of materials under high pressures and temperatures. These include a broad range of experimental techniques, such as radial diffraction in the diamond anvil cell (DAC), usage of the D-DIA deformation apparatus and, more recently, 3D x-ray diffraction in the DAC. Overall, we can now study the behavior of materials up to 300 GPa at ambient temperature, 70 GPa and 1500 K in the DAC and 20 GPa and 2500 K in the D-DIA. In most experiments, in-situ x-ray diffraction in used to extract quantitative texture information and elastic strains within the sample. The experimental data is then combined with self-consistent plasticity numerical models in order to understand the behavior of the material. In this presentation, I will show results on the hcp phase of Co deformed at 300 K between 0 and 42 GPa and results on the hcp phase of Fe deformed at pressures and temperatures reaching 19 GPa and 600 K. I will highlight how the combination of x-ray diffraction and EPSC modeling can be used to infer important information, such as the average stress within the sample, identify and constrain the plastic deformation mechanisms that were activated, and evaluate stress heterogeneity with the sample. In the last part of the talk, I will introduce techniques based on 3D x-ray diffraction and show how they can be used to constrain grain to grain stress heterogeneities and identify dislocations, in-situ, within a sample under high pressure. In the future, a combination of 3D methods and average techniques of the radial diffraction combined with self-consistent models will offer great opportunities to understand and model plastic behavior under pressure. [Preview Abstract] |
Wednesday, June 29, 2011 4:30PM - 4:45PM |
Q3.00002: Strength measurement using Diamond Anvil Cell under Static pressure Jae-Hyun Klepeis, Hyunchae Cynn, William Evans, Robert Rudd, Lin Yang, Luke Hsiung, Changyong Park, Olga Shebanova, Curtis Kenney-Benson, Stanislav Sinogeikin The pressure-dependence of the quasi-static yield strength of polycrystalline samples has been measured in the diamond anvil cell at high pressure (up to 80 GPa) and room temperature using an implementation of a non-hydrostatic technique used by Meade and Jeanloz [J. Geophys. Res. 93, 3261 (1988)]. Vanadium and Tantalum-Tungsten alloys are studied, including vanadium in the pressure range of a recently reported high-pressure phase. We introduce the use of \textit{in situ} synchrotron X-ray determination of the sample thickness and pressure. In addition we use a step-wise analysis approach to obtain the pressure-dependent strength under the Tresca yield criterion. The results are compared with those by the previous technique of Meade and Jeanloz. This work performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344. HPCAT use is supported by DOE-BES, DOENNSA, NSF, and the W.M. Keck Foundation. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Wednesday, June 29, 2011 4:45PM - 5:00PM |
Q3.00003: Strain mapping of diamond anvils under ultra-high pressure Wenge Yang Microbeam diffraction is a powerful tool to estimate the strength of materials under high pressure in diamond anvil cells by measuring the lateral pressure gradient and sample thickness. More importantly the strain distribution inside of a diamond anvil can provide key information for diamond deformation and failure mechanism, which will guide the new design of anvils for next generation of anvils to achieve the maximum static pressure capability beyond the pressure record. In this talk, we will present the preliminary results obtained from submicron resolution diffraction data of anvils and metal films in DAC. The future application for nanobeam diffraction will be discussed. [Preview Abstract] |
Wednesday, June 29, 2011 5:00PM - 5:15PM |
Q3.00004: Coherent diffractive imaging of gold crystal under high pressure Xiaojing Huang, Wenge Yang, Ross Harder, Ian Robinson Coherent Diffractive Imaging (CDI) with Bragg geometry is a unique method that is sensitive to strain distributions in crystals. With measured 3D diffraction intensities around Bragg peaks, 3D real-space images can be obtained by inverting these over-sampled diffraction pattern using phase retrieval algorithms. The reconstructed magnitude stands for physical electron density of the measured crystal, while the obtained phase structure represents lattice dislocations. We extend the capability of Bragg CDI to investigate crystal strains under high-pressure environment. We demonstrate the strain evolution of a gold crystal under various pressures. This technique opens the door to visualize strain-introduced phase transition driven by high pressure. [Preview Abstract] |
Wednesday, June 29, 2011 5:15PM - 5:30PM |
Q3.00005: The Effect of Crystallite Size and Texture on the Strength of MgGeO$_{3}$ Post-Perovskite Lowell Miyagi In-situ radial synchrotron x-ray diffraction is used to measure lattice strain and lattice preferred orientation (texture) in MgGeO$_{3}$ post-perovskite synthesized and deformed in the diamond anvil cell up to 135 GPa. Lattice strains are used to calculate differential stress supported by the sample and can provide a lower bounds estimate on yield strength. MgGeO$_{3}$ post-perovskite synthesized from the enstatite phase exhibits a weak transformation texture of (100) planes at high angles to the direction of compression. In a sample with larger crystallites, pressure increase and deformation results in (001) lattice planes orienting nearly perpendicular to compression, consistent with dominant (001) slip. In another sample with smaller crystallites it is difficult to induce texture change, and differential stress is higher than in the sample with larger crystallites. When MgGeO$_{3}$ post-perovskite is synthesized from the perovskite phase a different transformation texture of (001) planes at high angles to compression is observed. This sample is able to support large differential stress as the direction perpendicular to the (001) plane is a plastically hard orientation for MgGeO$_{3}$ post-perovskite. [Preview Abstract] |
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