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One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfNbVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x=12x-VCrMoMnFe, 12x+Sc, 12x+Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x+Be alloy reveals single-phase C14 structure with very high concentration of structural defects and ultra-fine dendritic microstructure with almost homogenous distribution of the constituted elements over the alloy matrix. The 7x and 12x+Sc alloys contain C14 as a main phase and unknown impurity phases. To characterize the materials, we examine their heat capacity, electrical conductivity and magnetic properties. The measurements reveal that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggests that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band. Analysis of the results suggests that the mechanism of Laves phase formation in multicomponent multi-principal element metallic alloys is may be the same as in polydisperse hardspheres mixtures. Another important conclusion is that the configurational entropy is a negligible factor in the stabilization of multi-element Laves phases.

Among the multiplicity of single-phase high-entropy alloys explored up to now, the TiZrHfNb one is accepted as thermally stable material that crystalizes into a single-phase body-centered cubic (BCC) solid solution. This HEA demonstrates exceptional structural stability at high temperatures, while its behavior under moderate thermal conditions (700 - 1300 K) has not been examined extensively so far. Here we address structure formation, phase transitions, thermal stability, and properties of the HEA under different thermal treatments. To do that, we synthesize the single-phase BCC structure and analyze its structural evolution its structure during long-time isothermal annealing as well as slow heating. In this study, we cover the temperature interval up to 1300 K and the annealing times up to 700 hours. In-situ X-ray diffraction combined with high-temperature measurements allow us to identify phase transformations in the HEA. It is revealed that BCC single-solid solution decomposes into several phases after isothermal annealing at 673 K for less than 200 hours. After prolonged homogenization, the system is a three-phase material consisting of two BCC and one HCP solid solutions. Ab initio simulations performed for the liquid phase reveal weak chemical interaction in the studied system and indirectly confirm the ability of the HEA to form single-phase solid solutions.

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 eutectoid decomposition of intermetallic CuZr under isothermal and nonisothermal conditions was studied by differential scanning calorimetry, electrical resistivity measurements, X-ray diffraction analysis, optical microscopy, and dilatometry. The kinetic diagram of the eutectoid decomposition of intermetallic CuZr was determined for the first time. The rate of the eutectoid decomposition of the CuZr phase was found to be one to two orders of magnitude lower than that in many other copper-based systems. The kinetics of the eutectoid decomposition under isothermal conditions was investigated, and the kinetic parameters of the decomposition were determined (the activation energy E a = 395 ± 24 kJ/mol and the Avrami constant n = 3.3 ± 0.1).

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.

The process of the eutectoid decomposition CuZr → Cu10Zr7 + CuZr2 in a Cu50Zr50 alloy under isothermal and non-isothermal conditions was investigated by using differential scanning calorimetry, electrical resistivity, X-ray diffraction, optical microscopy and dilatometer techniques. The continuous cooling transformation and time–temperature transformation diagrams for the decomposition of CuZr were determined over a wide temperature range. It was observed that the decomposition process is extremely slow in comparison with many other copper-based systems. The kinetics of the eutectoid decomposition under isothermal conditions was discussed within the frameworks of the Johnson–Mehl–Avrami theory. Kinetics parameters of eutectoid decomposition, namely the activation energy E a = 395 ± 24 kJ mol−1 and the power n = 3.3 ± 0.1 in Avrami exponent, were determined.

Differential scanning calorimetry, laser flash technique, dilatometry, and a method based on a rotating magnetic field were used to study for the first time thermophysical and electrical properties of the Cu50Zr50 equiatomic alloy in the quenched state and after annealing at temperatures ranging from room temperature to 1100 K. The thermal conductivity coefficient was calculated using the results of heat capacity, thermal diffusivity, and density measurements. The sequence and temperatures of structural transformations in the quenched Cu50Zr50 alloy were determined during alloy heating. The electron component of thermal conductivity was estimated using the Wiedemann–Franz–Lorentz law. This law was found to be satisfied well for the quenched sample at temperatures above 600 K and for the annealed sample at temperatures beginning from 900 K. As the temperature decreases, the lattice contribution increases. This fact indicates the marked effect of strong chemical interaction between copper and zirconium on the heat- and electrotransport processes.

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.

The temperature dependences of ultrasound velocity a in Pb-Bi melts are measured by a pulsedphase method. The measurements were performed in the temperature range between the liquidus temperature and 1400 K, as a rule, in cooling of a sample. The experimentally measured temperature dependences of the ultrasound velocity are used to calculate the polytherms of the adiabatic compressibilities of the alloys and to plot ultrasound velocity and adiabatic compressibility isotherms. The nonuniformity of the ultrasound velocity in the melts along the vertical coordinate has received much attention. This heterogeneity is explained in terms of a metastable melt heterogeneity.

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.

The authors gratefully acknowledge the financial support of the Russian Foundation for Basic Research under the contract 10-03-96043. This work was also supported by the projects VEGA 2/0111/11, APVV-0413-06, APVV-0647/10 and by the Centre of Excellence SAS FUN-MAT. This research contributes to the European COST Action MP0602 on Advanced Solder Materials for High Temperature Applications. The density values for Sn - Ag and Sn - Zn alloys with near eutectic compositions were determined by the gamma-absorption method both in the liquid and solid states. Sn-rich melts of the Ag-Sn system were found to be microheterogeneous, whereas Sn-Zn melts demonstrate the behavior typical for true solutions. (C) 2012 Elsevier B.V. All rights reserved.

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.

A method is suggested, which enables one to determine the interfacial tension on the interface between stratifying liquids using the equipment for measuring the ultrasonic velocity by the pulse-phase method. This method is employed for measuring the temperature dependences of interfacial tension in Ga-Bi and Ga-Pb systems in the monotectic to critical temperature range. The results are in good agreement with literature data.

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 temperature dependence of the density, the viscosity, the ultrasound velocity and attenuation and the magnetic susceptibility of the Pd–18 at.% Si alloy in liquid state have been measured. A difference during heating and subsequent cooling with a branching temperature at 1380–1430 K was observed for all measured quantities. An abnormally high attenuation of ultrasound was furthermore observed during several hours after that the sample was melted. The results are interpreted in terms of metastable inhomogeneities existing in the melt.

Temperature dependences of the density of Pd–Si alloys containing from 11 up to 33 at.% Si have been studied by means of the absolute method of penetrating γ- radiation in an interval from room temperature up to 1900 K. The accuracy of the measurement is ±0.6% and its resolution is within 0.2–0.3%. Liquidus and solidus temperatures of the investigated alloys ( T L and T S , respectively), density changes during melting ( Δρ ) and pre-crystallization overcooling (Δ T ) have been determined on the basis of the obtained data. T L and T S values are in good agreement with the known phase diagram of the system. Density and molar volume isotherms and also Δ ρ and Δ T concentration dependences have been plotted and demonstrate some anomalies near the stoichiometric composition of Pd 3 Si and in the concentration interval of easy amorphization of Pd–Si alloys.

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.

Measurements of temperature dependences of density d and ultrasound velocity V s of the eutectic Bi-44.6 wt.% Pb alloy were performed from eutectic temperature up to 550–900∘C. Density was studied using gamma absorption method. Ultrasound velocity was determined by pulse phase method. The dependences V s(T) and d(T) are linear in temperature interval of measurements and can be approximated by the equations: $$\displaylines{ V_{\rm s} (T) = 1788 - 0.269\;(T - 398)\ {\rm m} \cdot {\rm s}^{ - 1}.\cr d(T) = 10271 - 1.29\;(T - 398)\ {\rm kg} \cdot {\rm m}^{- 3} .\cr} $$ These results are found to be in good agreement with data of other works.

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.