Fine and coarse powders of diamond were mixed with Si and sealed in evacuated glass tubes to be HIP'ed at temperatures between 1300°C and 1600°C and at the pressure of 150MPa for 90min. The sintered materials were characterized by means of X-ray powder diffraction, microscope, SEM and EDS. Their densities and mechanical properties were measured. The sintering proceeded rapidly at temperature above 1400°C. The main reaction possibly takes place in the liquid state, because the melting temperature of Si is at 1410°C in air. The X-ray diffraction patterns were indexed by diamond, Si and SiC. No trace of conversion from diamond to graphite was observed. Among the starting materials prepared, the highest strength was found in the sample whose mixing ratio of fine and coarse diamonds and Si was 1:3:1 in weight. An application of the products to high pressure anvils was attempted and the generation of 7.70GPa in 6-8 split-sphere type apparatus was confirmed.
The pure and dense Ti3SiC2 material was tried to fabricate by two different approaches; HIP sintering of the SHS-derived Ti3SiC2 powders, and the reactive-HIP sintering of the mixed powders of Ti, SiC, and C. The product with the highest content of Ti3SiC2 consisted of 97.3vol% Ti3SiC2 and the remaining TiCx. This material was obtained by the reactive-HIP, carried out at 1500°C, 40MPa for 30min. The density was 99% of theoretical. The Ti3SiC2 grains had columnar and plate-like shapes, which included many stacking faults along the (001) plane. The Vickers hardness, Young's modulus, fracture toughness, and flexural strength were 4GPa, 283GPa, 11.2MPa √m, 410MPa, respectively. These mechanical properties are considered to be almost the intrinsic property of the bulk Ti3SiC2. The severe oxidation of the Ti3SiC2 started at about 1100°C. The electrical resistivity was 1.77×10-6Ωm at room temperature. It increased with increasing temperature, but showed the discontinuous change at around 1030-1040K. The Seebeck coefficient was 4-20μV/K in the range from 300K to 1200K. This small positive value suggests that the Ti3SiC2 is a semimetal with hole carriers.
B6O sintered compacts were prepared by high pressure and temperature treatments of in-laboratory synthesized B6O powder. Sinterable B6O powder with grain sizes of 1.2-1.4μm was formed above 1300°C in 4 hours in a pure argon stream by a solid-liquid reaction between amorphous boron and B2O3 powders. Single phase sintered compacts with relative densities above 95% were obtained under the sintering condition of 3-5GPa, 1700°C and 20min. The Vickers microhardness of the sintered compact was 31-33GPa. The B6O sintered compact exhibited an oxidation resistance in air up to 600°C and a mild oxidation behavior in the temperature range of 700-1000°C with the formation of a liquid protective film of B2O3.
Quantum stress on valence electron, named electron stress (σ), in K and Al has been calculated by using pseudopotential method under strict uniaxial strain deformation. Electron pressure (p) and electron stiffness parameter (c) have been defined from σ. Though some properties of simple metals are characterized from free electron gas, density of σ showed certain localization, like atomic bond. Changes of distributions on σ and p were discussed from Bain's bct structure path on fcc/bcc phase transformation. Rapid increases of σ were also observed. These peculiar spatial and quantity changes of σ might imply switching of atomic bond during fcc/bcc phase transformation.
High-pressure Brillouin scattering studies are described by presenting a total system for determinations of direction-dependent acoustic velocities, refractive index, adiabatic elastic constants, adiabatic bulk modulus, and elastic anisotropy in a simple molecular solid grown in a diamond-anvil cell. The detailed method is presented for an orientationally disordered phase III (1.0≤P≤3.5GPa) of a molecular solid NH3 at 300K. This phase III shows either the molecular rotation or the hydrogen bond. Typical values of three elastic constants are C11=21.1, C12=17.1, and C44=8.1GPa at P=2.56GPa. The elastic anisotropy, A=4.05 at 2.56GPa, is almost constant against pressure for fcc crystalline NH3. These properties are compared with those of solids CH4, Kr, H2S, HCl, and CO2, by concerning with the effects of the molecular rotation and the hydrogen bond under compression.
Pressure distribution under high pressure around 5GPa were measured in a diamond anvil cell for four kinds of pressure media, such as pyrophyllite etc. Lorentzian-like pressure profiles with different line width (FWHM) in each pressure medium were observed. The order of line width value was α-Fe2O3<pyrophyllite<NaCl<Cu. Pressure distributions obtained experimentally were simulated using rigid plastic FEM. Steep pressure distributions in pyrophyllite and α-Fe2O3 were well fitted on the assumption that friction factor m was proportional to the power of pressure until m=1. These results are expected to contribute to an efficient design of a high pressure apparatus.
High-pressure treatment was carried out for Al-based alloys in the range of room temperature to 1300°C. The pressure was applied up to 7GPa by using a cubic-anvil device. A cylindrical bulk sample was placed into a boron nitride capsule and inserted into a carbon tube heater. Metal disks were attached on the top and bottom of the heater for the electrical contact with an external power supplier. Pyrophyllite was used as a pressure medium to attain quasihydrostatic condition. (1) A large amount of impurity was introduced into the specimen from the metal disk when the specimen was molten. Such a trouble never occurred if the specimen was kept solid during the treatment. Since a few small cracks were inevitably produced in the capsule and the heater by pressing, the encapsuled liquid metal oozed from the capsule through them, reached the disk and reacted. Such contamination was avoidable when disks made of graphite was used. (2) The electric conductivity of the heater altered when the liquid metal exuded and contacted the heater. The corresponding signal can be sensitively detected by monitoring the voltage and current of heater when elevating temperature, indicating the emergence of liquid phase. It was applicable as the easy measurement of specific temperature in fusion-related phenomena such as melting and eutectic reaction.
Fe-3%Si alloy single crystals were deformed in tension along the  or  axis at 77K and 298K in order to study the necking behavior. Two types of deformation band, kink band and band of secondry slip were formed on necking section of specimens deformed at 298K along the  or  axis, respectively. Cell structure of dislocations in deformed single crystals appeared on the necking section in both axes. Such dislocation structure is supposed to influence non-uniform deformation of the crystals.
Influence of strain rates on the grain size dependence of tensile deformation behavior was investigated on a mild steel and solid-solute hardened 440MPa and 590MPa grade steels. The grain size of these steels was ranged from 0.005mm to 0.2mm in diameter. Tensile tests were performed at strain rates of 0.02/s and 2/s with an Instron tensile machine, and at 2000/s with a split-Hopkinson pressure bar apparatus. The relationships between yield strength and grain size of the steels investigated were well represented by the Hall-Petch relationship, and the energy absorbed during deformation at the strain rate of 2000/s increased for finer grain size. The grain size dependence of the yield strength of the 440MPa and 590MPa grade steels was intensified with increase in strain rate, while, those of the mild steel were almost independent of the strain rate. The n-value of the mild steel was remarkably reduced with an increase of the strain rate. The grain size, however, didn't affect the n-value.
In this paper, we investigate crack extension behaviors for a linear isotropic elastic body with two parallel interacting cracks at the neighborhood of the main crack tip. By using the E-integral which is path independent even for a path containing stationary crack tips, we compute the energy release rate for all the crack tips at the onset of crack kinking. As a result, assuming the isotropy of fracture toughness of the body and judging from the criterion based on the energy release rate, we find that there exist the relative positions of the interacting cracks which promote or interrupt the straight extension of the main crack and which make the main crack jump to an extension of an interacting crack.
The fretting fatigue properties of pearlitic and bainitic steel with medium carbon steel contact material were examined using the clamping contact double bridge pads system. In order to investigate the effects of contact pressure and relative slip amplitude on fretting fatigue strength, the fretting fatigue tests were carried out under the conditions of two contact pressures and three pad lengths. The fretting fatigue strength decreased with increasing contact pressure and with increasing pad length at the constant contact pressure of 98MPa. Also crack initiating position moved from the edge to the center of fretted damage surface with decreasing contact pressure. Interrupted fretting fatigue tests were carried out in order to investigate the fretting damage and the crack initiation at the pad length of 30mm and the contact pressures of 49, 98 and 196MPa. The saturation of fretting damage occurred beyond a certain number of fretting cycles, and the ratio of number of cycles to saturation of fretting damage was about 50 to 60% in the present conditions. And the ratio of number of cycles to crack initiation was less than 20% in this study.
It is well known that the strength characteristics of the glass used for the cathode ray tubes usually has a distinct scatter under the influence of surface flaws. Therefore, it is important to consider the variations in the static and delayed fracture strength of glass for the reliable design of vacuum cathode ray tubes under the atmospheric pressure. In this study, static and delayed fracture strength tests of glass were carried out using polished, abraded and scratched surface specimens in atmosphere in order to investigate the influence of the surface conditions on the strength characteristics statistically. From the goodness of fit test by the chi-square (x2) methed, the validity of the assumed distribution of the cumulative failure probability on the static and delayed fracture strength corresponding to each surface condition are discussed. Moreover, the statistical properties of the relationships between the static and delayed strengths are examined.
The viscosity of aqueous lithium chloride (LiCl) solution was measured at 0.1-375MPa, at 278.2-318.2K, and 0.5-4.0molkg-1. The Jones-Dole B coefficients for LiCl in water were obtained from the concentration dependence of the viscosity, and were divided into each ionic contribution. In the studied ranges of pressure and temperature, the B for Li+ ion decreases monotonically with increasing pressure. However, the B for Cl- ion increases with pressure up to 100-200MPa. Pressure dependence of the B for alkali metal ions (Li+, Na+, K+ and Cs+) were discussed supposing that the B consists of three terms, that is, Einstein effect (BE), dielectric friction effect for solvent (BD), and structural effect of solvent (BS).
Stress transfer parallel to the axis of high performance polyethylene fibers in a fiber reinforced epoxy resin composite was investigated by X-ray diffraction. Internal stress σf in the embedded fiber could be measured by monitoring the longitudinal strain of the crystalline regions of polyethylene by X-ray diffraction. The stress σf increased linearly with external stress applied to the composite. This behavior was in agreement with the rule of mixture of mechanical reinforcement and independent of interfacial adhesion. The mechanical reinforcement was dependent on the mechanical properties of both fiber and matrix, and also a fiber volume fraction. Interfacial adhesion and the existence of fiber ends influenced the mechanical properties of large deformation such as tensile strength. The “X-Ray Diffraction Method” proved to be a powerful tool for detecting the stress on the incorporated fiber in the loaded composite in situ and non-destructively.