Density and viscosity of molten Zn-Al alloys

Different Zn-Al alloys were applied in various hot-dip coating processes, such as galvanizing, GALFAN, GALVALUME, and aluminizing, for corrosion protection. Density and viscosity are two important parameters of the molten alloys in many studies, especially those involving fluid mechanics. However, the experimental data of these two important properties are scarce. Interpolation and extrapolation of experimental data are often necessary. Models that can describe the entire system are needed for the prediction of these properties at different temperatures and with different alloy compositions. Various thermodynamic models were examined in the current study, and the one that provided the best fit to the experimental data of the Zn-Al binary system was introduced.     

Evidence of clustering in liquid Zn-Sb alloys from viscosity measurements

Viscosity measurements have been performed on Zn-Sb alloys over the entire composition range employing the oscillating crucible technique. The viscosity showed a distinct maximum at Zn₄Sb₃ (43.86 at. pct Sb). The activation energy is high in the composition range from 40 to 50 at. pct Sb, but shows a local minimum at Zn₄Sb₃. The data suggests that tightly bound Zn₄Sb₃ clusters exist in the melt.     

The density and viscosity of liquid antimony

Absolute techniques have been used to determine, to a high degree of accuracy, the density and viscosity of liquid antimony. The data obtained are in reasonable agreement with previous work. Densities were measured up to about 115° above the melting point and varied linearly with temperature according to the equation p = 6.902-6.486 × 10^-4t wheret is in °. Viscosities were measured up to only 70° above the melting point and about 7° below on the supercooled liquid. The viscosity results were fitted to the Andrade equation ŋν^1/3 =A exp C/νT whereA and C are constants whose values were determined as 1.608 × 10^-3 and 221.4, respectively.     

Relation between viscosity and diffusion in amorphous metallic alloys

The main characteristics of creep and diffusion data in metallic amorphous alloys (PdSi and FeNiB types) are presented. It is shown that the “free volume model” cannot satisfactorily explain these data, particularly the different behaviour of diffusion and creep with respect to the kinetics of relaxation. Finally it is shown that the creep behaviour of metglas is qualitatively similar to that of polycrystals at high temperature and that, from a macroscopic point of view, Nabarro-Herring (or Coble) model are able to account for creep and diffusion experiments. We also discuss, from an atomistic point of view, the two defects which are involved in this model: equilibrium “diffusion” defect and sinks out of equilibrium.     

The density and surface tension of dilute liquid Na-In alloys and comparison with liquid Na-Cd alloys

The density and surface tension of five liquid Na-ln alloys, containing between 0.5 and 7 at. pct In, have been measured in the temperature range 170° to 400°C using a maximum bubble pressure technique which incorporates an automatic pressure measuring and recording device. The results are compared with corresponding data reported previously for Na-Cd alloys. The gram-atomic volumes of the Na-ln alloys, calculated from the densities, indicate a substantial contraction on alloying which is, on average, about double that for the Na-Cd alloys and qualitatively consistent with thermodynamic data for the two systems. The surface tension of liquid sodium is increased slightly on adding indium, indicating a lower indium concentration in the surface than in the bulk, in contrast to the marked surface active behavior of cadmium. The surface excess concentrations of indium and cadmium are calculated using Gibbs’ adsorption equation. The surface excess entropy, estimated from the temperature dependence of the surface tension, is compared and briefly discussed for the two systems.     

Density and solidification shrinkage of hypoeutectic aluminum-silicon alloys

The density of liquid and solid hypoeutectic aluminum-silicon alloys has been measured with high accuracy in the temperature range 400 °C to 800 °C by using the indirect Archimedian method. A eutectic mixture of KCl and LiCl salts was used as reference liquid. This method allowed measurements of density for both liquid and solid in the same experiment and thus reduced the systematic error in estimating the solidification shrinkage. The results show that the density of liquid aluminum-silicon alloy increases with increasing silicon content, while silicon reduces the density in the solid state. Silicon content reduces the solidification shrinkage from 6.6 pct for pure aluminum to 4.4 pct for Al-11.6 pct Si.     

Viscosities of indium-lead liquid alloys

The viscosities of indium-lead alloys have been determined by using the Ostwald type viscometer. The values have been obtained by a relative technique since the viscometer has been calibrated with indium and lead. Isothermal viscosities show that the negative deviations from ideal mixing decrease with increase in temperature. The results are studied from the stand-point of thermodynamics. The temperature dependence can be described by Arrhenius relation. The activation energy depends on concentration and is close to 1.6 kcal/mole. In the studied temperature range, it has been established that the data can be fitted with Arrhenius relation and Andrade’s equation.     

Thermal conductivity of liquid metals and alloys

The thermal conductivity data of liquid metals have been correlated based on the cell theory of liquids. The temperature dependence of thermal conductivity is predicted in the case of thirteen metals for which experimental data are available. The overall average absolute deviation of predicted values is 4.25 pct. The method has been extended to alloys.     

Densities of liquid Fe-Ni and Fe-Cr alloys

Formerly Graduate Student, Department of Materials Science and Engineering, Carnegie Mellon University.     

The density of liquid iron-carbon alloys

The density of liquid Fe-C alloys at temperatures ranging from 1250 °C to 1550 °C was measured by the sessile drop profile method. An accurate method of digital image processing was de-veloped to capture, enhance, and determine the coordinates of the X-ray shadow image of the droplet. Laplace's equation was then solved to obtain the volume and density of the droplet. The density of iron-carbon alloys was then determined as a function of carbon content (from 0 to 4 wt pct) and temperature (1250 °C to 1550 °C). A least-squares analysis of our data points gives an equation for the density of liquid iron-carbon alloys as a function of temperatureT [K] and carbon content [pct C] [wt pct]: ρ[g/cm³] = (7.10 - 0.0732[pct C]) - (8.28 - 0.874[pct C]) × 10^-4(T - 1823) These results will give a value to within ±1.5 pct of the data of Lucas, [3] Widawski and Sauerwald, [2] and the present work.     

Thermodynamic properties of liquid magnesium-bismuth alloys

Thermodynamic properties of liquid Mg-Bi alloys have been determined, employing galvanic formation and concentration cells. There was a fairly good agreement between data obtained by the two different types of cells. The partial thermodynamic functions exhibit a marked deviation from ideality, which has been interpreted as a consequence of the stable compound Mg₃Bi₂ being formed in the system. The experimental data have been treated according to Krupkowski to give equations for the activity coefficients of magnesium and bismuth. From these equations, together with phase diagram data, the Gibbs free energy of formation of solid Mg₃Bi₂ has been evaluated. A similar treatment also has been applied to literature data for the corresponding Mg-Sb system.     

Oxidation of liquid ternary bismuth-based alloys

The oxidation of liquid alloys Bi-Ag-Cu, Bi-Ag-Ge, Bi-Ag-Sn, Bi-Ag-Pb, Bi-Cu-Sn, Bi-Sn-Pb, and Bi-In-Pb in air is studied as a function of the alloy composition by high-temperature gravimetry. The compositions of the oxide layers that form on these alloys are determined.     

Thermochemistry of ternary liquid Cu-Mg-Si alloys

The thermodynamic properties of ternary liquid Cu-Mg-Si alloys with a constant concentration ratio of x _Cu/x _Si=7/3 were determined using a combination of different experimental methods. Enthalpies of mixing were measured by isoperibolic calorimetry, and magnesium vapor pressures were obtained by an isopiestic method. Partial thermodynamic properties of magnesium were derived from the vapor pressure data, and the composition dependence of the magnesium activities is given for 1173 K. Integral Gibbs energies of mixing for liquid alloys were calculated by a Gibbs-Duhem integration. The agreement of the thermodynamic data obtained from different methods was found to be very good.     

Thermodynamic parameters of liquid gold-aluminum alloys

Thermodynamic activities and, enthalpies for Au−Al alloys have been measured by Knudsen-cell mass spectrometry, independently using closely similar techniques in laboratories in Vienna and Strathclyde. The results are consistent and indicate, for Au rich alloys, gold activities with positive deviations from Raoult ideality. This is in disagreement with EMF measurements of Au activity previously reported; the results also indicate endothermicities (of ∼ 38 kJ/mol at _x Al ∼ 0.5) that are some 5 to 6 kJ/mol larger than those indicated by the EMF measurements.     

thermodynamic properties of liquid Ag-Si alloys

The thermodynamic properties of silicon in liquid Ag-Si alloys in the range of 1100 to 1325°C have been measured by an electrochemical cell employing silica-saturated lithium silicate as the electrolyte. The range of composition studied is 0.015 <x _Si < 0.29. For the change in standard state from pure liquid silicon to silicon at infinite dilution with the composition in atom fraction: Si(I) = Si (inf. dil.): △G° = 5,000 + 5.47T, (J/g-atom) The results of the study are in good agreement with the measurements on the phase diagram by Hager. Member of AIME; Visiting Scientist, Mass.(1969)