[en] Acoustic velocities, elastic constants and thermodynamic parameters upon pressure up to 2 GPa of typical Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 bulk metallic glass (BMG) have been studied by using a pulse echo overlap method. The results indicate that the glass forming ability (GFA) has a relation with the elastic constants for a glass forming system. The compression curve of the BMG is interposed among its components, and the BMG exhibits small volume changes upon pressure, confirming that the BMG has similar atomic close-packed configurations with elements which may closely related to the origin of its excellent GFA

[en] Using the pulse echo overlap method and the pulse superposition method, the acoustic velocities V_l, V_s and the attenuations α_l, α_s of Zr_41.2Ti_13.8Cu_12.5Ni_10.0Be_22.5 bulk metallic glass have been measured below 2 GPa with 10 and 20 MHz carrier frequencies, respectively. The results reveal that V_l and V_s increase linearly with increasing pressure (P); the slope of the V_l - P curve decreases with increasing frequency, while that of the V_s - P curve increases with increasing frequency. This means that there is a slight dispersion of sound under pressure. The attenuation increases obviously with the carrier frequency from 10 to 20 MHz. The effects of frequency on the velocity and attenuation under high pressure are discussed

[en] The longitudinal and shear velocities, and their pressure dependences, for various bulk amorphous materials, including bulk metallic glasses and non-metallic glasses, have been measured by the ultrasonic pulse echo overlap method under hydrostatic pressure (maximum: 2 GPa) or uniaxial compression in ambient conditions. The second- or third-order elastic constants and the long-wavelength acoustic mode Grueneisen parameter are calculated. The results reveal that all metallic glasses have positive pressure dependences of both the longitudinal and shear velocities, while for most non-metallic glasses both the longitudinal and shear velocities decrease with increasing pressure. Thus, the Grueneisen parameters evaluated for the mean mode and shear mode for metallic glasses and non-metallic glasses have opposite signs. This indicates that the influences of the short-range-order structure and bonding, correlating closely with the atomic configurations in the various amorphous materials, play an important role in the properties determined by vibrational anharmonicity. The negative and positive Grueneisen parameters exhibit mode softening and stiffness under high pressure, respectively. The results also clearly demonstrate that the Grueneisen parameter is affected by the pressure derivative of the shear modulus, especially for non-metallic glasses

[en] The structural evolution and property changes in Nd₆₀Al₁₀Fe₂₀Co₁₀ bulk metallic glass (BMG) upon crystallization are investigated by the ultrasonic method, x-ray diffraction, density measurement, and differential scanning calorimetry. The elastic constants and Debye temperature of the BMG are obtained as a function of annealing temperature. Anomalous changes in ultrasonic velocities, elastic constants, and density are observed between 600-750 K, corresponding to the formation of metastable phases as an intermediate product in the crystallization process. The changes in acoustic velocities, elastic constants, density, and Debye temperature of the BMG relative to its fully crystallized state are much smaller, compared with those of other known BMGs, the differences being attributed to the microstructural feature of the BMG

[en] The microstructure and its evolution of a Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 bulk metallic glass (BMG) annealed under high pressure and below glass transition temperature are investigated by using high resolution transmission electron microscope, differential scanning calorimeter, x-ray diffraction, ultrasonic study, and density measurements. It is found that high pressure annealing below T_g results in a microstructural transformation from short-range order to medium-range order in the BMG; the BMG with medium-range order structure exhibits different structural, thermal and acoustic properties

[en] Acoustic velocities and their temperature dependence of Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 bulk metallic glass (BMG) have been measured up to 773 K by using an ultrasonic pulse-echo overlap method. The temperature dependence of density, Vicker's hardness, elastic constants, and thermodynamic parameters of the BMG are determined. A rapid change of the density, acoustic velocities, elastic constants, and Debye temperature near the glass transition temperature, and anomalous density, acoustic and elastic behaviors in the supercooled liquid region are observed. A striking softening of long-wavelength transverse acoustic phonons in the glassy state relative to the supercooled liquid state is found. The glass transition process is delayed to high temperature with an increase of heating rate. Our results provide evidence that the glass transition in the BMG can be regarded as a kinetically modified thermodynamic phase transformation

[en] An ultrasonic pulse-echo method was used to measure the transit time of longitudinal and transverse (10 MHz) elastic waves in a Nd₆₀Al₁₀Fe₂₀Co₁₀ bulk metallic glass (BMG). The measurements were carried out under hydrostatic pressure up to 0.5 GPa at room temperature. On the basis of experimental data for the sound velocities and density, the elastic moduli and Debye temperature of the BMG were derived as a function of pressure. Murnaghan's equation of state is obtained. The normal behaviour of the positive pressure dependence of the ultrasonic velocities was observed for this glass. Moreover, the compression curve, the elastic constants, and the Debye temperature of the BMG are calculated on the basis of the similarity between their physical properties in the glassy state and those in corresponding crystalline state. These results confirm qualitatively the theoretical predictions concerning the features of the microstructure and interatomic bonding in the Nd₆₀Al₁₀Fe₂₀Co₁₀ BMG