Surface tension of liquid Au-Bi-Sn alloys

The surface tension of a promising lead-free solder Au-Bi-Sn alloys was investigated both by the sessile-drop method and calculation. Experimental measurements were carried out for two cross-sections with the constant gold to bismuth ration of 1:1 and 1:2. For all the investigated compositions, decrease of the surface tension is observed with increasing temperature. Meanwhile, the surface tension values were also calculated based on Butler's equation, with using the newest research on thermodynamics data of...     

Anomalous temperature dependence of the surface tension in liquid silver–lead alloys

The surface tension of liquid silver–lead alloys is discussed with special emphasis on the unusual temperature coefficients apparent at certain concentrations. In contrast to most other liquid alloys silver-rich mixtures of silver–lead adopt positive temperature coefficients. This anomalous behaviour is found to be well explained in terms of Butler's model of surface tension. The phenomenological approach of Bhatia and March was applied in semi-empirical manner in order to achieve agreement with the experimental findings. In view of the high concentration fluctuations of the system – expressed in terms of S_cc(0) – the anomalous temperature coefficients find a plausible interpretation. A short critical assessment of the model's general applicability to systems with demixing properties is presented. Qualitatively, both treatments indicate that the unusual temperature dependence of the surface tension is the mere consequence of the thermodynamics of the system.     

The dynamic viscosity of liquid Cu–Si alloys

The dynamic viscosity of liquid Cu–Si alloys is measured in the Cu-rich composition range (up to 40 at.% Si). The Arrhenius-law describing the temperature dependence of the viscosity holds for all alloys investigated. The viscosity isotherms, both experimental and from thermodynamic model calculations, show a broad maximum covering the homogenity ranges of the intermetallic phases. An interconnection of such findings with the atomic structure of the liquid alloys is briefly discussed.     

Thermodynamic properties of liquid glass-forming Ca–Mg alloys

The complex formation model was used to investigate the thermodynamic properties of liquid Ca–Mg glassy alloys. Our expressions reproduce the thermodynamic functions such as free energy of mixing, enthalpy of mixing, entropy of mixing and activity ratio. The study of long wavelength concentration–concentration fluctuations (S_CC(0)) provides structural information about liquid glass-forming Ca–Mg alloys. Chemical short range order parameter (₁) was obtained from S_CC(0) to quantify the degree of order. The study reveals that the formation of more than one type of complex may be related to the process of glass formation.     

The Ag–Cu–Ge ternary phase diagram

The Ag–Cu–Ge phase diagram is not very well elaborated. In this work an attempt is made to validate the phase diagram in the area of the ternary eutectic and to decide whether it is a suitable model system for solidification experiments. The different steps in the solidification sequence are separately discussed and analysed. It is shown that an optimization of the system is necessary. The experiments in this work demonstrate that the transition reaction Ge is located closer to the ternary eutectic than assumed in earlier work.     

Internal friction of Cu–CuAlO alloys

Polycrystalline internal oxidize copper alloy with CuAlO particles has been studied by isothermal mechanical spectrometry, above room temperature. The frequency range was 10⁻⁴ to 30 Hz and the maximum strain 2×10⁻⁵. Experiments were carried out on a sample after 18% cold-rolling and successive annealings at various temperatures. The internal friction spectra obtained between 290 and 400 K exhibit only a low frequency background superimposed to a non thermally activated maximum. After annealing at 400 K, the background decreases, a relaxation peak appears and its maximum rises progressively as temperature increases. The relaxation parameters, obtained from the frequency shift of the maximum with temperature, leads to E_a=0.9 eV, and τ₀=6.9×10⁻¹⁰ s. These values are similar to those described in the literature for a relaxation peak assigned to dislocation motion inside grains.     

Surface tension and wetting behaviour of molten Bi–Pb alloys

The present work represents an experimentally based investigation on the surface properties of molten Bi, Pb and Bi–Pb alloys. The surface tensions of the two pure elements and of seven alloys were measured by the sessile-drop method over the temperature range 623–773 K. In addition the wetting behaviour of the eutectic Bi–Pb alloy on AISI 316L substrate was also investigated in the same temperature range. The results obtained show general agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values obtained by the application of the compound formation model (CFM).     

Theoretical calculations of the surface tension of Ag(1−x)-Cu(x) liquid alloys

The surface tension of silver-copper binary liquid alloys is calculated, in the frame work of Eyring theory. The calculations were made for different compositions (mole fraction, x_Cu = 0, 0.2, 0.4, 0.6, 0.8 and 1), in the temperature range 1100-1800 K. The surface tension decreases with temperature increase, at a fixed copper fraction x_Cu, and increases with increasing copper content. The calculated results are appropriately compared with existing literature data.     

Microstructural simulation of phase decomposition in Cu–Ni alloys

The microstructure simulation of spinodal decomposition was carried out in the aged Cu–70 and 90 at.% Ni alloys, based on a solution of the non-linear Cahn–Hilliard partial differential equation by the finite difference method. The calculated concentration profiles were compared with the experimental ones determined by atom-probe field ion microscope analyses of the solution treated and aged Cu–70 at.% Ni alloy samples. Both the numerically simulated and experimental results showed a good agreement for the concentration profiles and microstructure evolution in the aged Cu–Ni alloys. A very slow growth kinetics of phase decomposition was observed to occur in this type of alloy. The morphology of decomposed phases consists of an irregular shape with no preferential alignment in any crystallographic direction. The wavelength of composition modulation was determined numerically to be about 2 nm and it remained constant after aging at 573 K for times as long as 8889 h. No phase decomposition was observed to occur for the numerical simulation of aging at temperatures lower than 523 K for a time as long as 1 year.     

Heat capacity of liquid and undercooled liquid metals and alloys

Trends in the dependences on temperature and concentration of experimentally determined heat capacities of liquid and undercooled liquid metals and alloys are discussed. A new adiabatic calorimeter for determining the heat capacity of liquid alloys up to 1500 K is described. The ability of several approximations and models to describe the different characteristics of the heat capacity of liquid and supercooled liquid metals and alloys is demonstrated.     

Similar and dissimilar friction welding of Zr–Cu–Al bulk glassy alloys

The friction welding of three kinds of Zr–Cu–Al bulk glassy alloys (BGAs) which show eutectic or hypoeutectic compositions to similar and dissimilar BGAs and crystalline metals has been tried. The shape and volume of the protrusion formed at the weld interface were investigated. In order to characterize the friction welded interface, micrographic observation and X-ray diffraction analysis on the weld cross-section were carried out. A successful joining of Zr–Cu–Al bulk glassy alloys to similar and dissimilar BGAs was achieved without occurrence of crystallizations at the weld interface through the precise control of friction conditions. In addition, the joining of Zr₅₀Cu₄₀Al₁₀ BGA to crystalline alloys was tried, but it was only successful for specific material combinations. The residual strength after welding of dissimilar BGAs was evaluated by the four-point bending test.     

Magnetic investigations in liquid Al–In

Measurements of the magnetic susceptibility in liquid alloys of indium with 0–20 at% aluminium are reported. Within the investigated range of temperature and composition all alloys are found to be diamagnetic. The increase of the magnetic susceptibilty due to the addition of aluminium follows a simple linear mixing law. The departures from the free electron behavior are analyzed in terms of the interactions between the electrons and the ion cores and the effect of exchange-correlation between the electrons. The potentials of the cores are indicated to have a very small influence on the electronic part of the susceptibility whereas electronic exchange-correlation yields enhancements of 20% at all compositions. The ambiguity due to the divergent estimates for the contributions of the diamagnetic cores to the total susceptibility is briefly discusssed.     

Experimental and calculated liquid-liquid interfacial tension in demixing metal alloys

Liquid-liquid interracial tension in binary and temary Al-based monotectic systems has been determined experimentally with a tensiometric method in a wide temperature interval. The temperature dependence of the interfacial tension is well described by a power law function of the type σαβ - （1 - T/Tc）δ with the critical exponent δ= 1.3 and a critical temperature Tc. Theoretical models describing the liquid-liquid interface in monotectic alloys and their applicability for calculation of the interfacial tension and its temperature dependence in binary systems are considered.     

Surface and transport properties of Cu-Sn-Ti liquid alloys

The lack of experimental data and / or limited experimental information concerning both surface and transport properties of liquid alloys often require the prediction of these quantities. An attempt has been made to link the thermophysical properties of a ternary Cu-Sn-Ti system and its binary Cu-Sn, Cu-Ti and SnoTi subsystems with the bulk through the study of the concentration dependence of various thermodynamic, structural, surface and dynamic properties in the frame of the statistical mechanical theory in conjunction with the quasi-lattice theory （QLT）. This formalism provides valuable qualitative insight into mixing processes that occur in molten alloys.     

Effect of Ce addition on the microstructure and damping properties of Cu–Al–Mn shape memory alloys

The effect of rare earth element Ce addition on the microstructure, martensitic transformation, mechanical properties and damping behavior of the Cu–Al–Mn shape memory alloys (SMAs) had been investigated. It is shown that the Ce addition makes the grain refinement and affects the martensitic transformation temperature. The tensile strength and the ductility of the Cu–Al–Mn alloys can be enhanced by the Ce addition. Damping capacity tan δ of the martensite for the Cu–Al–Mn–Ce alloys is strain amplitude dependent. The Ce addition has obvious effects on the damping properties of the martensite. With the increase of the Ce content, the damping capacity increases initially and then decreases.     

Variables on the precipitation of an intermetallic phase for liquid phase sintered W–Mo–Ni–Fe heavy alloys

The concentration of Mo in the liquid phase of W–Mo–Ni–Fe heavy alloys during isothermal hold dictates the precipitation of an intermetallic phase during cooling. If the concentration of Mo atoms in the matrix phase exceeds an equilibrium value (between 8 and 9 at.%), Mo atoms have a strong tendency to precipitate along with W, Ni and Fe from the matrix phase onto the solid matrix phase interface during cooling. The coprecipitation of W, Mo, Ni, and Fe results in the formation of an intermetallic phase in the interface between the solid grains and the matrix phase, (W₄Mo₆)(Ni₇Fe₃), which possibly has the same structure as MoNi. This intermetallic phase is difficult to eliminate by a fast water-quench practice.     

Interface structure and energy in Cu–71.8 wt.% Ag

The as-cast eutectic Cu–71.8 wt.% Ag was prepared. The orientation relationship and interface structure of Cu and Ag phases were investigated using high-resolution transmission electron microscopy. The interface energies and nucleation rates in the formation of different orientation relationships were discussed. The Cu and Ag eutectic lamellae can form the cube-on-cube and hetero-twin orientation relationships and the occurrence probabilities of the two orientation relationships are approximate in the solidification of the eutectic structure. There are misfit dislocations and monolayer steps at the interface between both phases having the cube-on-cube or hetero-twin relationship. The twin fault and lattice mismatch energies at the interface result only in an insignificant effect on the formation of different orientation relationships between both phases of the eutectic laminae.     

Ordering potential in liquid Al–Ge alloys structure and thermodynamics

In this paper we use the concept of ordering potential to calculate the atomic structure and the thermodynamic asymptotic limit of the liquid Al–Ge alloy, for which we previously measured the atomic structure and the electrical resistivity. The sign of the ordering potential in the region of the first nearest neighbours indicates whether the alloy is homo or hetero-coordinated. The aim of this work is to reproduce quantitatively the atomic structure by using the simple phenomenological Silbert-Young effective potential. This model can explain both the shape of the structure factor measured by neutron diffraction and the low-angle limit of the Bhatia–Thornton partial structure S_CC(q) given by thermodynamic measurements.     

毛细管法测量液体表面张力的误差分析与特性研究

通过Bashforth—Adams方程获得了真实接触角,在此基础上分析了毛细管法测量液体表面张力的误差来源,解决了这一领域存在的一些争议性问题,并进一步揭示和探讨了毛细管法测量液体表面张力的特性。