V. A. Bykov

Thermophysical properties of Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy

The thermophysical properties of the Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy in a wide range of temperatures from room temperature to 1000°C have been studied by the methods of differential scanning calorimetry, the laser flash method, and dilatometry. The obtained data on heat capacity, thermal diffusivity, and thermal expansion have been used for calculating coefficient of thermal conductivity. The sequence and temperatures of structural transformations during heating of the alloy have been established. It has been shown that the studied alloy possesses a coefficient of thermal conductivity that is 3.5–4 times smaller than that of pure titanium.

Magnetic properties and structure of nanocrystalline FINEMET alloys with various iron contents

The effect of the composition and annealing temperature on the structure and magnetic properties of soft magnetic nanocrystalline Fe-Cu-Nb-Mo-Si-B alloys has been studied. An increase in the iron content compared to that in the traditional FINEMET alloy is shown to allow one to increase the magnetic induction by 18% at a coercive force of no less than 6 A/m. It has been found that, along with the amorphous phase, rapidly quenched ribbons of alloys enriched in Fe contain crystalline α-Fe-based phase precipitates, the (100) crystallographic directions of which are perpendicular to the ribbon plane. Thermomagnetic analysis and differential scanning calorimetry were used to determine the temperatures of structural and magnetic phase transformations of the alloys with different iron contents. It was found that the separation of amorphous phase into areas of different compositions precedes the precipitation of nano-sized soft magnetic Fe-Si phase grains in the rapidly quenched iron-enriched ribbons.

Thermophysical and electrical properties of equiatomic CuZr alloy

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.

Magnetic susceptibility of dilute Al-Dy alloys at high temperatures

The magnetic susceptibility of Al-Dy alloys with the dysprosium content from 0.1 to 2.0 at % in the temperature range 300–1850 K has been studied. It is established for all compositions that the susceptibility begins to increase when the alloy temperature exceeds the melting temperature of the Al2Dy compound, and the concentration curves exhibit oscillations of the same type in the solid and liquid states. The experimental results are interpreted in terms of the existence of chains composed of Al2Dy quasi-molecules in the alloys.

Thermodynamic properties of melts based on the Al-Sm system

The equilibrium composition and thermodynamic characteristics of melts based on the Al-Sm system were studied by thermodynamic modeling using the ideal solution model of reaction products over the whole range of compositions 0 ≤ xAl ≤ 1 in argon at a total pressure of 1 atm and temperatures from 1873 to 2100 K.

Thermal Properties of CuGa2 Phase in Inert Atmosphere

Thermal decomposition of copper digallide was studied using experimental (thermal analysis) and theoretical (thermodynamic modeling) methods. The temperatures of CuGa2 incongruent melting are in satisfactory agreement between experimental and calculated values. Small differences with the phase diagram can be explained by minor non-stoichiometry of the alloy samples. The experimental studies of thermal diffusivity and thermal expansion of CuGa2 were performed in the temperature range 298-500 K. The heat conductivity coefficient was further calculated using literary data concerning the density and heat capacity of the copper digallide.

Thermal conductivity of Al–Gd–TM glass-forming alloys

Abstract Thermal diffusivity, specific heat capacity and thermal conductivity of Al86Gd6TM8 (TM = Cu, Ni, Co, Fe, Mn, Cr, Ti, Zr, Mo, Ta) glass-forming alloys in the temperature range of 300–880 K were determined by laser flash method. The temperatures of endothermic and exothermic reactions of the alloys were determined by differential scanning calorimetry method. The alloys were prepared by conventional arc-melting technique under helium atmosphere. All the alloys studied exhibit strong supercooling of the liquidus temperatures up to 80 K, which indicates their good glass-forming ability. The specific heat capacity of the alloys achieves the Dulong–Petits value in the temperature range of 350–550 K except Al86Cr8Gd6 and Al86Zr8Gd6 compositions. The values of both thermal diffusivity and thermal conductivity of the alloy studied are significantly lower than those for pure aluminum. It is found that embedding 14% (mole fraction) of transition elements (Gd+TM) in the aluminum matrix leads to significant decrease in the absolute magnitudes of both thermal diffusivity and thermal conductivity in crystalline state. The thermal conductivity of glass-forming Al86Gd6TM8 alloys is strongly affected by directed chemical bonding between alloy components.

Structural and Magnetic Peculiarities of Al 86 Ni 8 Sm 6 Alloy in Amorphous, Crystalline, and Liquid States

Magnetic, structural, and thermal characteristics of the Al86Ni8Sm6 alloy in amorphous, crystalline, and liquid states have been studied over a wide temperature range of 4–1900 K. It has been found that the amorphous alloy has a pronounced cluster structure with an average cluster size of 2–3 nm. The crystallization process occurs in four stages and no apparent thermal effect at the glass-transition temperature is observed. The amorphous ribbon has no magnetic order up to 4 K but demonstrates superparamagneic behavior. An analysis of isothermal magnetization curves indicates a possible correlation between structural and magnetically ordered clusters. Anomalous changes in the magnetic susceptibility in the liquid state have been found at temperatures substantially higher than the liquidus temperature; the anomalies indicate structural changes in the melt. The magnetic susceptibility in the amorphous, crystalline, and liquid states was found to be characterized by a high Van Vleck paramagnetic contribution and can be described adequately in terms of the classic Van Vleck theory with allowance for mixed valence effects. The obtained results are interpreted using a concept on the existence of a specific covalent-metallic interaction between aluminum and rare-earth metal atoms.

An automated setup for measuring the viscosity of metal melts

An automated setup for measuring the kinematic viscosity of metal melts using the method of damped torsional oscillations is described. The experimental errors in the viscosity determination are evaluated. The influence of the values of the damping factor, the oscillation period, and the sample radius and height on the value of the calculated viscosity error is analyzed. The methodological errors that are related to the consideration of the free-surface curvature, the thermal expansion, and the external friction in the inert atmosphere of the suspension system were analyzed. It is shown that these errors may have a significant effect on the viscosity determination accuracy. The viscosity of liquid lead in the range from the melting point to 1200°C is determined. The obtained data agree well with the literature data.

Effect of Titanium Additions on the Thermophysical Properties of Glass-Forming Cu 50 Zr 50 Alloy

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.