Search

For the first time, the electrical resistivity of liquid Cu64.5Zr35.5, Cu50Zr50, and Cu33.3Zr66.7 alloys at temperatures up to 1600 K has been measured by the contactless method in a rotating magnetic field. The measurements were taken during cooling in a helium atmosphere with a purity of 99.995%. The error of the electrical resistivity determination did not exceed 5%. It has been found that the electrical resistivity of liquid Cu64.5Zr35.5, Cu50Zr50, and Cu33.3Zr66.7 alloys decreases linearly with increasing temperature, while it increases with temperature for liquid copper and zirconium. The concentration dependences of the electrical resistivity and its temperature coefficient have a maximum at 55 at % and a minimum at about 60 at % Zr, respectively. These concentration dependences are similar to the dependences obtained for amorphous alloys and are explained in the framework of the Ziman theory.

Differential scanning calorimetry, laser flash method, and dilatometry were used to study the thermophysical properties of quenched Cu50Zr50–xTix (x = 0, 2, 4, 6, 8) alloys in the temperature range from room temperature to 1100 K. Data obtained on the heat capacity, thermal diffusivity, and density have been used to calculate the coefficient of thermal conductivity. Temperatures corresponding to the stability of martensite CuZr phase, its eutectoid decomposition, and formation in Cu50Zr50–xTix alloys with different Ti contents upon heating have been determined. It has been found that the thermal diffusivity and thermal conductivity of the studied alloys are low and a typical of metallic systems. As the titanium content increases, the coefficients of thermal conductivity and thermal diffusivity vary slightly. It has been shown that the low values of thermophysical characteristics correspond to the better capability of amorphization and can be a criterion for the glass-forming ability of Cu–Zr-based alloys.

We systematically study peculiarities of the martensitic transformation (MT) in (Cu0.5Zr0.5)100−xAlx glass-forming alloys focusing on the Cu46Zr46Al8 one. We obtain that an addition of aluminum to ...

The temperature dependences of the density, the dynamic viscosity, the ultrasound velocity, and the electrical resistivity of the liquid lead–bismuth eutectic are investigated over a wide temperature range. Anomalies in the temperature dependences of the ultrasound velocity and the resistivity are found at 580 K. These anomalies are associated with the formation of groups of bismuth atoms near the eutectic temperature. The isothermal and adiabatic compressibilities are determined for the first time over a wide temperature range.

In the temperature range of T = 300–1900 K, covering the crystalline and liquid states, the electroconductivity, thermal diffusivity, thermal conductivity, density and magnetic susceptibility of Al 83 Co 10 Ce 7 glass-forming alloy were studied. It is established that the values of electrical and thermal conductivity of the system investigated are relatively low (in comparison with pure aluminum). Analyzing temperature dependence of Lorentz function obtained, we found that the lattice contribution in total thermal conductivity is essential. In liquid state above T > 1700 K, the anomalous changes in electroresistivity and magnetic susceptibility of the alloy were revealed. These high-temperature anomalies are accompanied by neither detectable thermal effects nor significant changes of alloy density. It was found that the density of the alloy investigated is greater for the liquid state than for the solid one. The experimental results obtained are discussed in the frames of conjecture about existence of chemically interacting Al 2 REM associates in the melt.

The method of penetrating gamma-radiation was used to measure the density of copper-aluminum melts containing from 0 to 100 % aluminum in the range of temperatures from liquidus to 1300–1400 °C; the concentration dependences of their molar volume were calculated as well. High accuracy of measurements (error not exceeding 0.2 %) allows using the values as reference data. Substantial non-monotonicity of the molar volume isotherms that proves the complexity of the specified melts especially in the area of compositions rich in aluminum was found. The parameters of polynomials describing concentration dependencies of the molar volume with the error not exceeding 1 % are presented.

The absolute method of penetrating gamma radiation has been used to measure temperature dependence of density for the Cu-Al alloys, which contain 0 to 100 at % of one of the components, in the temperature range between room temperature and 1300-1400 degrees C. Based on the experimental values of density, the parameters of the linear approximation of its temperature dependence have been calculated. These parameters have been used then to calculate values of density at certain values of temperature and to plot density isotherms. Density jumps at melting for the specimens have also been determined.

This work was supported by the Russian Foundation for Basic Research, project no. 10-03-96043-r_Urals_a. Temperature dependencies of density (by the gamma-penetrating method), electrical resistivity (by the contact-less method in rotating magnetic field), and magnetic susceptibility (by the Faraday method) of Sn-Bi alloys with near-eutectic compositions are investigated. The alloy with eutectic composition, Sn -58% (mass) Bi, is shown to differ significantly in the electron structure from hypo- and hypereutectic ones. The melt overheating above the given temperature provides the hysteresis of the properties sensitive to electron structure.

This study was supported by the Russian Foundation for Basic Research (project nos. 09-08-00040a and 07-08-00589a). The pulse-phase method is used for measuring the velocity of sound in liquid lead and bismuth and in lead-bismuth eutectic in the range from the melting temperature to 1380 K. The purity of investigated metals is 9.99% by mass or better. The confidence error of experimental results does not exceed 0.3%. The experimental data are compared with those available from the literature.

Using a phase pulse method for ultrasound velocity measurement, the kinetics of meniscus movement in the course of the hypermonotectic Ga–30 at.%Pb and Ga–40 at.%Pb melts separation was measured. Assuming that the process is limited by sedimentation of Pb-rich particles, their size distribution at various temperatures was determined. The time dependences of the volume fraction of dispersed particles and degree of sedimentation were calculated based on the experimental results. It was shown that coagulation of the particles is sufficient for surface energy reduction in the phase separation process.

This study was supported by the Russian Foundation for Basic Research (project nos. 09-08-00040a, 07-08-0589a, 09-08-01212 and 10-08-00802). The pulse-phase method, the gamma-attenuation method and the method of dumping oscillation of a crucible with a melt were used for measuring the velocity of sound, the density and the kinematic viscosity of a set of liquid-metal coolants for perspective nuclear reactors. There are liquid gallium, indium, tin, lead, bismuth and lead-bismuth eutectic alloy among the melts investigated. The accuracy of the measurements was as high as 0.3%, 0.2 to 0.4% and 1.5% for the ultrasound velocity, the density and the viscosity, correspondingly.

A set of acoustic (using the pulse phase method for ultrasound velocity v (s) measurement) and gamma-absorption experiments with the Ga-Bi melts have been performed to clear the nature of their microinhomogeneity. Both methods allow determining upsilon (s) and intensity of the penetrating gamma-beam, I, at various distances, h, from the bottom of the measuring cell. Distinct upsilon (s)(h) and I(h) dependences were discovered in one phase domain of the phase diagrams. It is clear that such inhomogeneity is connected with the chemical inhomogeneity of the melt which, in its turn, can exist if one of the components forms very large particles containing 10(4)-10(5) atoms. The cupola-like borders of the domains where such inhomogeneity exists were fitted in the phase diagrams of the systems under investigation. The inhomogeneity has been confirmed in special acoustic experiments with superposition of ultrasound and low-frequency oscillation.

This work was supported by the United States Department of Energy, Office of Basic Energy Sciences as follows: efforts at the Ames Laboratory were supported under Contract No. DE-AC02-07CH11358 and use of the Advanced Photon Source was supported under Contract No. DE-AC02-06CH11357. We present a new semi-empirical potential suitable for molecular dynamics simulations of liquid and amorphous Cu-Zr alloys. To provide input data for developing the potential, new experimental measurements of the structure factors for amorphous Cu64.5Zr35.5 alloy were performed. In this work, we propose a new method to include diffraction data in the potential development procedure, which also includes fitting to first-principles and liquid density and enthalpy of mixing data. To refine the new potential, we used first-principles and liquid enthalpy of mixing data published earlier combined with the densities of liquid Cu64.5Zr35.5 measured over a range of temperatures. We show that the potential predicts a liquid-to-glass transition temperature that agrees reasonably well with experimental data. Finally, we compare the new potential with two previously developed semi-empirical potentials for Cu-Zr alloys and examine their comparative and contrasting descriptions of structure and properties for Cu64.5Zr35.5 liquids and glasses.

The method of damped torsional vibrations of crucible with liquid under investigation is used for measuring the temperature dependences of kinematic viscosity ν of Cu100 − x Al x melts (x = 0–100 at.%) in the range of temperatures t between the liquidus and 1100–1450°C. Unlike the majority of such experiments, the measurements are performed both in the process of heating the sample after its melting and in the course of subsequent cooling. The branching of ν(t) curves corresponding to the foregoing modes is revealed below certain temperatures dependent on the composition of sample (viscosity hysteresis). The curves obtained under cooling have a simple exponential shape predicted by activation theories of viscous flow. The obtained temperature dependences are used for constructing isotherms of kinematic viscosity, on which maxima are observed in the vicinity of stoichiometric concentration of CuAl3 and composition of Cu-30 at.% Al. For the same compositions, extrema are observed on the concentration dependence of activation energy of viscous flow.

The absolute method of penetrating gamma radiation is used to measure the temperature dependences of density of Pd-Si alloys containing 11 to 33 at.% Si in the range from room temperature to 1600 degrees C. The resultant data are used for determining the liquidus and solidus temperatures of investigated alloys, the variation of their density in melting, and pre-crystallization cooling which corresponds to the cooling rate of 2 degrees C/min.

The author is thankful to the Russian Foundation of Basic Researches for the financial support of the work in frames of grants NN 06-03-90568 and 07-02-96045. Density d temperature dependences of Ga-Bi melts with 0, 10.2, 16.2, 29.8, 42.0, 51.6, 61.5, 80.0 and 100 at.%Bi were measured using absolute gamma-absorption technique with accuracy of 0.2 to 1.5% (depending on bismuth concentration). In addition, temperature dependences of ultrasound velocity v(s) were determined for the samples with 11.0, 16.7, 29.8 and 100 at.% Bi. The accuracy in the acoustic measurements was higher than 0.3%. The special scanning equipment for the gamma-densitometer has allowed to measure density of co-existing phases below the separation cupola. The obtained values coincide with reference data within the declared accuracy. An anomalous behavior of ultrasound velocity (deviation of the v(s)(T) from linear dependences) and significant increase of ultrasound attenuation were discovered for the samples with 16.7 and 29.8 at.% Bi at the temperatures of 70 to 100 K above the separation cupola. Using the experimental data, the thermal expansion coefficient, molar volume and adiabatic compressibility were calculated. All theses characteristics demonstrate linear behavior similar to ideal solutions.