Surface Tension Of Liquid Alloys Research Articles

Density and Surface Tension of Fe-Cu Melts

Fe-Cu alloys are used as structural materials for manufacture of large machine parts subjected to shock loads. Fe-Cu alloys have a higher corrosion resistance in a humid atmosphere and in salt solutions than cast steel. Fe-Cu alloys have high enough damping characteristics. Upon cooling the Fe-Cu melts is stratified into two phases before crystallization which in field of gravity are separated by density. It is possible to suppress delamination and obtain a material with structure of a “frozen emulsion” by heating melt to the temperature T* determined for each composition by a specific way. In this paper, we studied surface tension of liquid alloys of Fe-1wt.% Cu, Fe-20wt.% Cu, and Fe-30wt.%Cu in order to determine the temperature T*. For the melt of Fe-20wt.% Cu value T*=1670°C is highest. It is confirmed by results of measuring temperature dependence of surface tension. Temperature dependence of the surface tension Fe-Cu melts is characterized by a positive value of the temperature coefficient of surface tension dσ/dT which is abnormal for metal melts. Experimental data on the density, the surface tension of Fe-Cu liquid alloys have of independent metrological importance for practical foundry.

Effect of cerium on wettability of mechanically milled Cu-based brazing alloy powder

CuSn powders and TiH2 powders were milled using high energy mechanical milling to prepare Cu-based alloy powders for brazing diamond. And Ce was added to the milled Cu-based alloy powders to improve the wettability. It is found that the wetting angle reaches the minimum value 13.2° and the maximum spreading area 178 mm2 is achieved when the amount of Ce is 0.75 wt%. And Ce remarkably reduces the surface tension of liquid alloy, which improves the climbing height along the diamond and forms a massive support profile. And the results show that Ce can effectively improve the transverse rupture strength (TRS) due to high wettability. The wear characteristics of the diamonds brazed with Cu-based alloy containing 0.75 wt% Ce mainly consist of integrity, micro-fracture, fracture and rubdown, diamonds pull-out can not easily happen.

Evaluation of the Surface Tension of Silicon-Gold Binary Liquid Alloy

The gold-catalyzed vapor-liquid-solid (VLS) method is widely used for silicon nanowire (Si NW) fabrication. As the VLS process is influenced by the physical properties of the catalytic silicon-gold (Si-Au) droplet, quantifying the surface tension of the liquid alloy is important to achieve better control of the wire growth. Because the experimental measurement of the surface tension is difficult, it is necessary to obtain reasonable estimates from computational models. In this work, we conducted molecular dynamics simulations with a modified embedded-atom potential developed for the Si-Au binary system, and evaluated the surface tension γ based on the Virial stress expression. The dependence of surface tension γ on the Si fraction χ and temperature T is predicted. The entropy of the liquid-vapor interface was extracted from the slope of the γ-T curve. The Si concentration and stress distributions near the surface are also predicted. Our surface tension evaluation enables theoretical predictions of droplet and nanowire shape, and provides physical inputs for continuum phase field models of VLS growth.

A model for the prediction of liquid–liquid interfacial energies

A model for the calculation of liquid–liquid interfacial energies is presented. It is based on the assumption that the interface can be treated as a separate thermodynamic phase. Its derivation has been performed in an analogous way as the derivation of the Butler equation for the surface tension of liquid alloys. It requires as input parameters the excess free energy and the compositions of the bulk phases as functions of temperature. In addition, it also requires the partial molar volumes of the components. Comparison with existing experimental data for Al–Pb, Al–In, and Cu–Co in a non-equilibrium state shows very good agreements. For Al–Bi, the experimental data are either over or underestimated by a factor of ≈1.7, depending on which of the two thermodynamic assessments is used. For the Al-based systems, the calculated Al-mole fraction in the interface layer is close to the arithmetic average of the Al-mole fractions of the bulk phases.

Prediction of Surface Tension of Liquid Alloys and Molten Ionic Mixtures

Prediction of Surface Tension of Liquid Alloys and Molten Ionic Mixtures

Surface tension and density of liquid In–Sn–Zn alloys

Using the dilatometric method, measurements of the density of liquid alloys of the ternary system In–Sn–Zn in four sections with a constant ratio Sn:In=24:1, 3:1, 1:1, 1:3, for various Zn additions (5, 10, 14, 20, 3 5, 50 and 75at.% Zn) were performed at the temperature ranges of 500–1150K.Density decreases linearly for all compositions. The molar volume calculated from density data exhibits close to ideal dependence on composition.Measurements of the surface tension of liquid alloys have been conducted using the method of maximum pressure in the gas bubbles. There were observed linear dependences on temperature with a negative gradients dσ/dT. Generally, with two exceptions, there was observed the increase of surface tension with increasing content of zinc.Using the Butler's model, the surface tension isotherms were calculated for temperatures T=673 and 1073K. Calculations show that only for high temperatures and for low content of zinc (up to about 35at.%), the modeling is in very good agreement with experiment. Using the mentioned model, the composition of the surface phase was defined at two temperatures T=673 and 973K. Regardless of the temperature and of the defined section, the composition of the bulk is very different in comparison with the composition of the surface.

An investigation of the density and the surface tension in liquid Ag–Bi–Sn alloys

The density and surface tension of liquid alloys of the ternary system Ag–Bi–Sn were measured by a sessile drop method at temperatures up to 1,000 K. The investigation concentrated on sections of constant Ag/Bi composition ratios. Both quantities show a linear decrease with the temperature. The experimental surface tensions are in acceptable agreement with the calculations based on the thermodynamic activities of the components in the system. Over a wide range of composition the surface tension is not dramatically increased by the presence of Ag in the alloys which results presumably from the preferential occupancy of the surface layer by atoms of Bi and Sn. The non-simple variation of the densities with the composition points to a reduction in volume due to the mixing process which is discussed with particular regard to the literature data on the binary system Ag–Bi. The volume effects are indicated to occur predominantly near the Ag corner of the ternary system.

Surface properties of alloys and ionic mixtures

We have applied thermodynamic databases, which are generally used for the evaluation of phase diagrams and chemical reactions in multicomponent systems, to the calculation of the surface tension of liquid alloys, molten salt mixtures and molten slag. In addition, phase diagrams in nanosized particle alloy systems, which are affected by the surface energy, are also shown with some models and procedures to evaluate the above surface properties.

Effect of La content on microstructure evolution of 20Ag–Cu–Zn–Sn–P–La filler metals and properties of joints

The influence of La content on the microstructure evolution of 20Ag–Cu–Zn–Sn–P (wt-%) filler metals and the mechanical properties of joint was investigated in this study. The typical microstructure of filler metal was analysed by means of scanning electron microscopy, optical microscopy and X-ray diffraction. Microstructural observation indicated that the growth of crystal grains in filler metals was prohibited with increasing the La content. It was found that 0·1–0·3 wt-%La improved the wettability of filler metals on 321 stainless steel and Cu substrates. From mechanical properties tests, the shear strength increased with increasing the La content in the range of 0·1 to 0·5 wt-%. When the La content reached 0·5 wt-%, the maximum of the joint shear strength was achieved. When the content is proper, the La addition had a positive effect on wettability by reducing surface tension of liquid alloys.

Non-monotonic behaviour with concentration of the surface tension of certain binary liquid alloys

The surface tension σ(c) of most liquid binary alloys usually varies with concentration c in a monotonic way between the values σ1 and σ2 of the two pure metals, and this behaviour is well explained by current models. Some alloys show deviations from this ideal behaviour. One of those is Fe–B. The surface tension of this liquid alloy shows a minimum at 17 atomic % B, which corresponds well with the composition of the eutectic point in the phase diagram, followed by a maximum at a concentration of 24 atomic % B or higher. The usual models for the surface tension of liquid binary alloys do not explain those exceptional features, and we propose that a model involving the concentration fluctuations in the liquid alloy has the proper ingredients to account for the features in Fe–B and similar alloys.

Surface Tension of Liquid Alloys—A Thermodynamic Approach

A formula is derived to describe the surface tensions of binary and dilute multicomponent alloys such as iron alloys. It was thermodynamically proved that the surface tension can be described by a function of the concentrations of the alloy components in bulk phase through the use of thermodynamic parameters. The formula was applied to the binary alloys, Fe-O-N and Fe-O-S systems. The described surface tensions were found to be in good agreement with the measured values.

New Method for Rapid Detection of Surface Tension of Liquid Alloy and Its Application in Foundry Engineering

New Method for Rapid Detection of Surface Tension of Liquid Alloy and Its Application in Foundry Engineering

Effect of carbon and sulphur on the surface tension of molten iron

Surface tensions of Fe‐4%C‐S alloys were measured at 1623 and 1823 K using the sessile drop technique. Thermodynamic models based on Butler's equation for surface tension of liquid alloys have been compared with experimental results. Calculated values are found to be in good agreement with those of the experimental data of the system. At the same sulphur activity, the effect of carbon on the surface tension of Fe‐C‐S alloys was found to extrude only when the sulphur content was less than 0.005 %.

Use of Thermodynamic Data to Determine Surface Tension and Viscosity of Metallic Alloys

During the last three decades, various thermodynamic databases have been compiled to be applied mainly to the calculation of phase diagrams of alloys, salts, and oxides. The accumulation and assessment of thermodynamic data and phase-equilibrium information to establish those databases is sometimes called the CALPHAD (calculated phase diagram) approach. The CALPHAD approach has been recognized as useful in various aspects of materials science and engineering. In addition to the use of thermodynamic databases for the calculation of phase diagrams, it would be very desirable to apply them to the calculation of other physicochemical quantities, such as surface tension. By doing this, not only can the Utility of databases be enlarged, but also a deeper understanding of the physical properties in question can be reached.On the basis of the concepts just mentioned, we have applied those thermodynamic databases to the calculation of the surface tension of liquid alloys and molten ionic mixtures. In these calculations, we have applied Butler's equation for the surface tension of liquid alloys. In addition, we have modified Butler's equation to be extended to molten ionic mixtures by considering the relaxation structure in the surface. These approaches will lead us to develop a multifunctional data-bank System that will be widely applicable in the evaluation of physicochemical properties of liquid alloys and molten ionic mixtures from thermodynamic data.In this article, we explain some physical modeis for the surface tension and viscosity of liquid alloys and molten ionic mixtures, in which thermodynamic data can be directly applied to evaluate these physical properties. In addition, the concept for the just-mentioned multifunctional thermodynamic data-bank System will be described by demonstrating the simultaneous calculation of phase diagrams, surface tension, and viscosity of some alloys used for new, Pb-free soldering materials.

Application of a thermodynamic database to the calculation of surface tension for iron-base liquid alloys

Thermodynamic models based on Butler's equation for surface tension of liquid alloys has been discussed. In alloys, in which activities of components deviate largely from Raoult's law, the calculated surface tensions are found to be affected by the selection of the ratio of the coordination number in the surface phase to that in the bulk phase. Then, the surface tension of liquid Fe-Al, Fe-Co, Fe-Cr, Fe-Mn, Fe-Mo, Fe-Ni, Fe-Si, Fe-Ti and Fe-W binary alloys and liquid Fe-Cr-Ni ternary alloys have been calculated from thermodynamic data in a database constructed by Kaufman. The calculated results reproduce the concentration dependence of the surface tension in those alloys reported so far, but their absolute values are dependent upon the selection of surface tension values for pure elements