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C Yang,
W P Chen,
R P Liu,
Z J Zhan,
M Z Ma, W K Wang,
X D Wang,
Q P Cao,
J Z Jiang,
C Lathe,
H Franz
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ABSTRACT: Crystallization of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) prepared by shock-wave quenching under high-temperature and high-pressure has been examined by in situ synchrotron radiation x-ray diffraction. The first precipitated phase is found to be the same at different pressures, but the subsequent phase precipitation sequences are different. The crystallization temperature of the BMG increases with pressure, but with a sudden drop at about 6.0 GPa. The different phase precipitation sequences and the sudden drop in the crystallization temperature can be explained by complex pressure effects on the atomic configuration of the BMG.
Journal of Physics Condensed Matter 11/2007; 20(1):015201. · 2.55 Impact Factor
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C. YANG,
C. Z. FAN,
Y. Z. JIA,
X. Y. WANG,
X. Y. ZHANG,
H. Y. WANG,
Q. JING,
G. LI,
R. P. LIU,
L. L. SUN,
J. ZHANG, W. K. WANG
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ABSTRACT: The damage characteristics of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass under planar shock wave have been investigated by firing aluminum projectiles using a two-stage light
gas gun. The SEM results show that radial and symmetric cracks formed on the shocked plane of the sample at the impacted location
by aluminum projectile at the velocity of 2.7 km·s–1. Parallel shear crack/bands in the sublayer under the shocked plane were formed. For a better understanding of the response
features under shock wave, hypervelocity impact tests with conventional sphere aluminum projectiles were carried out. Besides
the same adiabatic shear crack/bands and crack propagations, craters were formed and lamination cracks occurred.
07/2006: pages 217-223;
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ABSTRACT: Compositional and microstructural differences from bottom to top along a water-quenched Zr41Ti14Cu12.5Ni10Be22.5 alloy rod, 90 mm in length and 22 mm in diameter, were investigated experimentally by x-ray diffraction measurement, differential scanning calorimetry, and composition analysis. The results show that the upper part of the rod contains more beryllium atoms and is amorphous. The lower part with less beryllium atoms contains crystalline phases. The composition gradient is possibly due to the gravity-driven transport of Be-rich clusters and un-melted tiny solid pieces in the alloy melt.
Journal of Materials Research. 08/2005; 20(09):2302 - 2306.
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ABSTRACT: Planar shock compression effects on void formation and cracking in Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) are studied in this paper. Cracking was found to be a result of void linkage in some direction deviation from the maximum shear stress plane. Changing the state of the stress inside the BMG sample led to formation of different void distribution. Nucleation of the microvoids was possibly initiated by release of excess free volume under shock wave compression.
Journal of Materials Science 07/2005; 40(15):3917-3920. · 2.02 Impact Factor
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ABSTRACT: Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) was prepared by shock-wave quenching. Differences in property, structure, and thermal stability were found between the BMGs prepared by the shock-wave quenching and water quenching. The glass transition temperature of the shock-wave-quenched BMG is about 13 K higher than that of the water-quenched one. Although the density of the shock-wave-quenched BMG is decreased, the acoustic velocities in it are increased. Shock-wave quenching is possibly a promising method for preparing BMG.
Applied Physics Letters 07/2005; 87(5):051904-051904-3. · 3.84 Impact Factor
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ABSTRACT: Embedded in a flux of dehydrated B2O3, melts of pure germanium were undercooled by repeated melting and solidification of the specimens within a differential scanning calorimeter facility. The highest undercooling obtained in this way was 190 K. The specific heat of the undercooled melt was measured by calorimetric diagnostics within the facility, and showed a linear dependence on temperature. The thermodynamic properties of germanium, such as the difference of Gibbs free energy, the difference of entropy, and the difference of enthalpy between the undercooled melt and the solid state, were derived from the measured specific heat.
Applied Physics Letters 07/2004; 85(4):558-560. · 3.84 Impact Factor
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Journal of Materials Science Letters 01/2003; 22(3):171-173.
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ABSTRACT: The pressure dependence of the acoustic velocities of a Pd 39 Ni 10 Cu 30 P 21 bulk metallic glass have been investigated up to 0.5 GPa at room temperature with the pulse echo overlap method. Two independent second-order elastic coefficients C 11 and C 44 and their pressure derivatives are yielded. The vibrational anharmonicity is shown by calculating both the acoustic mode Grüneisen parameters in the long-wavelength limit and the thermal Grüneisen parameter, and this result is compared with that for the Pd 40 Ni 40 P 20 bulk glass.
J. Phys.: Condens. Matter. 01/2003; 15:101-107.
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ABSTRACT: Structural changes in bulk metallic Zr41.2Ti13.8Cu12.5Ni10Be22.5 glass subjected to heat treatments under high pressure were investigated by means of synchrotron radiation x-ray diffraction (SRXRD). In situ SRXRD measurements showed that the crystallization process of this material is comprised of two stages. Subsequent heating at 10 GPa converts the sample from the amorphous (Am) phase into a metastable fcc phase and then leads to the fcc phase changing back to the Am phase, indicating that there is a kind of 'reversible' phase transition phenomenon occurring in the alloy. Such phenomenon is explained on the basis of free energy considerations.
Journal of Physics Condensed Matter 10/2002; 14(44):11243. · 2.55 Impact Factor
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ABSTRACT: The compression behaviour of a Pd 39 Ni 10 Cu 30 P 21 bulk metallic glass is investigated at room temperature up to 23.5 GPa using in situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. Pressure induced structural relaxation of the bulk metallic glass is exhibited within the pressure range. It is found that below about 5 GPa, the existence of excess free volume contributes to rapid structural relaxation, which gives rise to rapid volumetric change. Under higher pressure, further relaxation results in structural stiffness.
J. Phys.: Condens. Matter. 01/2001; 13:5743-5748.
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ABSTRACT: Acoustic velocities of Pd39Ni10Cu30P21 bulk metallic glass ~BMG! are measured by an ultrasonic
technique upon annealing. The elastic constants and the Debye temperature are obtained. A large
softening of the transverse phonon is exhibited in the as-quenched BMG relative to its crystallized
state. Upon crystallization, the shear modulus and the Debye temperature increase by ;30% and
;12%, respectively; however, the density increases by only ;0.6%. Some anomalous acoustic and
elastic behaviors are observed near the glass transition temperature and in the supercooled liquid region of the BMG. The anomalies are explained with regard to the structural changes.
Applied Physics Letters. 01/2001; 77:1147.
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ABSTRACT: The pressure-dependent acoustic velocities of a Pd39Ni10Cu30P21 bulk metallic glass ~BMG! have
been measured up to 0.5 GPa by using an ultrasonic technique with the pulse echo overlap method.
The elastic constants, the Debye temperature, and their pressure dependence are obtained. The
isothermal equation of state ~EOS! of the BMG is established in terms of the Murnaghan form. The
atomic configurations of the BMG are discussed by comparing the elastic constants and the EOS with those of its metallic component and of other amorphous materials.
Applied Physics Letters. 01/2000; 77:3734.
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ABSTRACT: A new type Cu–La2O3 composite was fabricated by internal oxidation method using powder metallurgy. Sliding wear behavior of the Cu–La2O3 composites was studied by using a pin-on-disk wear tester under dry sliding conditions with or without electrical current, rubbing against GCr15 type bearing steel disk at a constant sliding speed of 20 m/s. The influence of varying applied load and electrical current was investigated. The worn surfaces were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to determine the wear mechanisms. The results showed the Cu–La2O3 composites had an electrical conductivity of 81.9% IACS (International Annealed Copper Standard, 100% IACS = 58 MS/m) and a hardness of HV105. The wear rate of the Cu–La2O3 composite pins increased with the increase in the electrical current at high sliding speed. The main wear mechanisms of the Cu–La2O3 composites were found to be adhesive wear, abrasive wear and arc erosion.
Wear.
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ABSTRACT: Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass rods with an aspect ratio of 25:1 were prepared by suction casting and water quenching methods. A suitable temperature region for super-plastic deformation of the bulk metallic glass was determined by thermal expansion experiments, and the bulk metallic glass was found to exhibit excellent super-plastic deformation ability in this temperature region.
Materials Science and Engineering: A. 359:402-404.
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ABSTRACT: Solidification of 0.1–1.0 mm diameter droplets of Al–50 at.%Si hypereutectic alloy was achieved in a 3 m drop tube. Phase morphologies of deeply etched sections of the solidified samples with different diameters are examined. With decreasing of the diameter of the droplets, refinement of the primary silicon phase is observed. A tendency for the primary silicon crystals to form granular morphology is found in the smaller samples. Stratified deposits of aluminum in the primary silicon along the silicon plate are evident in bigger samples, but less evident with decreasing of the sample size. Morphologies of Al–Si eutectics change from needle-like to short, blunt and worm-like forms with decreasing of the sample size. Through calculation of the nucleation rates at different sizes of the solidified sample and analyses of the crystal morphologies, grain refinement of the primary silicon can find its origins of copious nucleation during rapid cooling and solute-restriction to crystal growth.
Materials Science and Engineering: A.
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J. Appl. Phys. 99(2006),023525.
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C Yang,
W-P Chen,
R.P. Liu,
Z.J. Zhan,
M.Z. Ma, W. K. Wang,
X D Wang,
Q.P. Cao,
J.Z. Jiang,
C. Lathe,
H. Franz
J. Phys. Condens. Matter 20(2008),015201.
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ABSTRACT: Bearing rollers, 7.5 mm in diameter and 7.5 mm in length, were prepared from Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG). The working life of the bearing rollers was evaluated through a real rotation test with a large-load and at a high-speed, and compared with that of commercial GCr15 steel rollers. The results show that the bearing rollers of Zr-based bulk metallic glass have a better wear resistance than the commercial GCr15 ones. And the wear behaviors are different for these two kinds of bearing rollers.
Materials Science and Engineering: A.
