Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session G2: Material Science I |
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Chair: Chris Adams, Los Alamos National Laboratory Room: Fairmont Orchid Hotel Amphitheater |
Tuesday, June 26, 2007 10:30AM - 10:45AM |
G2.00001: High-pressure phase synthesis of Si using femtosecond laser-driven shock wave Tomokazu Sano, Masashi Tsujino, Norimasa Ozaki, Tomoaki Kimura, Ryosuke Kodama, Akio Hirose, Osami Sakata, Masayuki Okoshi, Narumi Inoue High-pressure phases of silicon are synthesized using femtosecond laser-driven shock wave. The crystalline structure in a recovered sample was determined using synchrotron x-ray diffraction and electron diffraction methods. The high- pressure phase with simple hexagonal structure exists in the recovered sample. The metastable BC8 structure also exists. The temperature profile in the shock wave as a function of the pressure was estimated using the thermodynamic theory. The estimated results agree well with the experimental results. [Preview Abstract] |
Tuesday, June 26, 2007 10:45AM - 11:00AM |
G2.00002: Dynamic mechanical behavior of boron carbide-based composites Shmulik Hayun, Nahum Frage, Moshe Dariel, Eugene Zaretsky This presentation is concerned with the dynamic response of two types of boron carbide-based composites. The composites were fabricated by infiltration of compacted but unsintered B$_{4}$C preforms and of partially sintered B$_{4}$C skeletons by liquid Si. During the infiltration process, molten silicon reacts with the B$_{4}$C phase resulting in the formation of the SiC and B$_{12}$(B,C,Si)$_{3}$ phases. Some residual silicon is also present in the infiltrated composites. The dynamic behavior was studied in planar impact experiments (impact velocities 100-1000 m/sec) using a 25 mm gas gun. The velocities of the sample-PMMA window interface were monitored continuously by VISAR. The composites failed completely in compression, at loads above their HEL (17-18 GPa). The spall strength, deduced from low-velocity impacts, ranged from 0.5 to 1.1 GPa, depending on the tensile strain rate. Scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) were used to analyze the fracture surface. The correlation between the microstructure of the infiltrated composites and their dynamic response is discussed. [Preview Abstract] |
Tuesday, June 26, 2007 11:00AM - 11:30AM |
G2.00003: Shock compression properties of hard materials Invited Speaker: Through the measurement of Hugoniot parameters, we can get useful information about high-pressure phase transition, equations of state (EOS), etc. of solids, without pressure calibration. We have performed the Hugoniot-measurement experiments on various kinds of hard materials of calcogenides, oxides, nitrides, borides by using a high time-resolution streak camera system (inclined-mirror method) to investigate the yielding property, phase transition and EOS. It was found that almost all brittle materials behave as an elasto-isotropic solid unlike metals (elasto-plastic solid), except a very few materials such as TiB$_{2}$. We observed the shock-induced phase transitions on ZnS, ZnSe, TiO$_{2}$, ZrO$_{2}$, Gd$_{3}$Ga$_{5}$O$_{12}$, AlN, B$_{4}$C, etc. Some oxide materials showed virtually incompressible EOS's in the high-pressure phase region. Here, the Hugoniot-compression data are reviewed, and the yielding property, phase transition and EOS of these hard materials are discussed. The applications for anvil materials, shock-resisted materials, etc. are also discussed. [Preview Abstract] |
Tuesday, June 26, 2007 11:30AM - 11:45AM |
G2.00004: Comparison of High Strain Rate Properties of Tantalum Processed by Equal Channel Angular Pressing Philip Flater, Joel House, James O'Brien, William Hosford Current ingot refinement and solidification techniques used in tantalum processing often result in inconsistent mechanical properties. Subsequent processing by equal channel angular pressing (ECAP) has been shown to reduce or eliminate internal structural variations as well as part-to-part variability [Hartwig, 2006]. This paper investigates the effects of ECAP processing on the properties of tantalum. The materials of interest are 2.5-inch round bar tantalum supplied by H.C. Starck and Cabot Supermetals. Three metallurgical conditions were examined for each material: as worked, fine-grain annealed, and large-grain annealed. Prior to annealing, each bar was processed eight times through a 135 degree ECAP die using route Bc then forged into 0.25-inch plates. Specimens were then removed from the plates. Mechanical properties were evaluated using low- and high-rate uniaxial compression experiments. Specimen load axis were oriented either through-thickness or in the plane of the original plate. Wave propagation and anisotropy were studied using the Taylor impact experiments. The experimental results and physical and mechanical characterization will be discussed. [Preview Abstract] |
Tuesday, June 26, 2007 11:45AM - 12:00PM |
G2.00005: Shock compression of magnesium silicon nitride Toshimori Sekine, Takamichi Kobayashi, Bert Hintzen Magnesium silicon nitride is a ternary nitride compound with an orthorhombic, distorted wurtize structure at ambient condition. There is no study on this material at high pressures, but a recent theoretical work predicts phase transitions at $\sim $17 GPa. We have determined Hugoniot for magnesium silicon nitride ceramics up to 150 GPa and performed recovery experiments up to $\sim $50 GPa. The Hugoniot measurement indicates HEL of 15-17 GPa and a compression curve with no clear phase transition. The compression curve, however, showed a gradual deviation from the compression curve calculated for the low-pressure phase with increasing pressure. If this is the case, there would be a sluggish phase transition at high pressure. We carried out a series of recovery shots on the powders mixed with copper, but the results indicated no additional phase. We compared the results with the theoretical prediction. [Preview Abstract] |
Tuesday, June 26, 2007 12:00PM - 12:15PM |
G2.00006: Laser-induced damages to sapphire single crystals Pedro Peralta, Sheng-Nian Luo, Chi Ma, Dennis Paisley Sapphire ($\alpha$-Al$_2$O$_3$), an important optical material, has often been used as a substrate or window in laser-induced shock wave loading of condensed matter. Systematic experiments were conducted to investigate its breakdown threshhold, spall and fracture, plasticity, melting and recrystallization, upon $\mu$s laser pulse illumination on the (0001) surface (wavelength of 1054 nm). One of the surfaces of the cylindrical specimen was coated with Al and graphite. The recovered samples were examined with microscopic analytic techniques. At sufficient laser fluxes, fracture was induced; the fracture patterns on the uncoated surface correlated with the spatial distribution of the driving pulse, and demonstrated three-fold symmetry as expected for the (0001) surface. Plastic deformation and solid$-$solid phase change were also characterized. On the coated side, the ultrafast heating and quenching yielded melting, vitrification, and nanocrystalline hexagonal and cubic phases. [Preview Abstract] |
Tuesday, June 26, 2007 12:15PM - 12:30PM |
G2.00007: Phase transitions, high-rate straining and fracture of iron under spherical explosive loading. A.V. Petrovtsev, E.A. Kozlov, C.A. Brichikov, V.V. Dremov, G.V. Kovalenko, D.A. Varfolomeev, A.M. Bragov, A.K. Lomunov, A.V. Dobromyslov, N.I. Taluts, A. Juanicotena, M. Gatulle, C. Voltz Processes that occur in iron compressed in spherical systems are characterized by: a wide range of thermodynamic and straining parameters depending on a distance from the center; polymorphous and phase transitions; spall fracture nucleation, development and re-compaction; varying energy cumulation conditions as a response to changes in the loading amplitude and duration. That is why spherical shock experiments are an important source of information and a complex test for models. The paper describes iron models developed on the basis of time- resolved measurements in planar and wedge experiments and in mechanical tests. It presents results of numerical simulations of spherical explosive recovery experiments where the size of spheres and loading parameters were varied. The features of high-rate straining in different spherical layers and their dependence on the loading parameters, EOS and elastic-plastic and fracture models were analyzed. Calculated results were compared with those of the material science investigation of recovered samples. [Preview Abstract] |
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