Prediction of thermodynamic properties of ternary liquid solutions including metal alloys

The free-volume theory of liquid solutions formulated by Flory and also by Patterson for binary systems, has been extended to ternary systems. Numerical calculations have been performed to test the validity of the approach, for a system of organic liquids, for a system of condensed gases, and also for a system of liquid metal alloys. Satisfactory results have been obtained in all cases. Thus, prediction of properties of ternary solutions from a limited number of data concerning pure components and binary mixtures was found possible.     

Calculation of the viscosity of liquid Ag- and Au-based alloys: a pseudopotential approach

The viscosity of liquid alloys of Ag–In, Ag–Ge, Ag–Sn, Ag–Sb, and Au–Sn is analyzed in terms of a pseudo-potential method with special emphasis on its variation with the composition. The computational problems associated with the divergence of the key quantities of the theory are solved by presuming the oscillating part of the effective potential to decay exponentially with the distance. The disregard of the influence from neighbor atoms at distances of more than 10 times the hard core diameter is not believed to have an essential impact on the results. All systems under investigation show negative deviations from the additive law which complies well with the experimental findings. The predictions from a semi-empirical model based on simple physical quantities are also taken into consideration. The good overall agreement suggests that the semi-empirical model offers a useful, in many circumstances, more accessible alternative.     

A first-principles thermodynamic approach to ordering in binary alloys

The communication reviews the augmented space based approaches to thermodynamics and ordering of binary alloys. We give several examples of metallic alloys to illustrate our methodology.     

Study of thermodynamic properties of carbon nanoparticles by the laser heating method

A new experimental approach to the analysis of thermodynamic properties of amorphous carbon nanoparticles synthesized via hydrocarbon pyrolysis behind shock waves is discussed. The proposed approach is based on the analysis of thermal radiation of nanoparticles heated by a laser pulse. The sublimation temperature of the carbon nanoparticles might be determined by the two-colour pyrometry; their sizes, by laserinduced incandescence; and the volume fraction of the sublimated substance, by the laser extinction method. The sublimation temperature depends on both the particle size and the temperature conditions of their formation. The value of surface energy for amorphous carbon nanoparticles was estimated.     

Superconducting properties of amorphous Zr-Ge binary alloys

A new type of refractory metal-metalloid amorphous alloys exhibiting superconductivity has been found in a binary Zr-Ge system by a modified melt-spinning technique. Specimens are in the form of continuous ribbons 1 to 2 mm wide and 0.02 to 0.03 mm thick. The germanium content in the amorphous alloys is limited to the range of 13 to 21 at%. These amorphous alloys are so ductile that no cracks are observed even after closely contacted bending test. The Vickers hardness and crystallization temperature increase from 435 to 530 DPN and from 628 to 707 K, respectively, with germanium content, and the tensile fracture strength is about 1460 MPa. Furthermore, the amorphous alloys exhibit a superconducting transition which occurs very sharply. The superconducting transition temperature (T _c) increases with decreasing germanium content and reaches a maximum value of 2.88 K for Zr₈₇Ge₁₃. The upper critical magnetic field for Zr₈₇Ge₁₃ alloy was of the order of 21.8 kOe at 2.0 K and the critical current density for Zr₈₅Ge₁₅ alloy was about 175 A cm^–2 at 1.70 K in the absence of an applied field. The upper critical field gradient atT _c and the electrical resistivity at 4.2 K increase significantly from 24.6 to 31.5 kOe K^–1 and from 235 to 310cm, respectively, with the amount of germanium. The Ginzburg-Landau (GL) parameter and the GL coherence length §_GL (0) were estimated to be 72 to 111 and about 7.9 nm, respectively, from these experimental values by using the Ginzburg-Landau-Abrikosov-Gorkov (GLAG) theory and hence it is concluded that the Zr-Ge amorphous alloys are extremely soft type-II superconductor with high degree of dirtiness which possesses theT _c values higher than zirconium metal, in addition to high strength combined with good ductility.     

Amorphous binary alloys obtained by oxido-reduction in the liquid phase or by electrolysis

The preparation by oxide-reduction in liquid phase and electrolysis of amorphous alloys of nickel-phosphorous is examined. They take the form of films deposited on glass, powder and thick layers formed on copper foils. Their composition and some of their characteristics such as local order, crystallization, electrical and magnetic properties are measured.     

基于铝热反应Cu-Fe二元合金的微观组织与摩擦性能研究EI北大核心CSCD

基于铝热法制备含2%(质量分数)Al的Cu-Fe合金,采用XRD,SEM,EDS和EBSD技术对Cu-Fe合金的相结构、微观组织进行表征,同时采用HVS-1000A维氏硬度仪和CFT-1材料表面性能测试仪测试Cu-Fe合金的硬度及抗磨损性能。结果表明:利用铝热反应可高效地制备Cu-Fe合金,成分可控,组织致密无夹杂,其中Fe相均匀地分布在Cu基体中,Cu和Fe的相界面结合良好;Fe相的硬度为322.2HV,基体Cu相的硬度为169.3HV,Cu-Fe合金的电导率为40.8 MS/m。铝热法制备的Cu-Fe合金具有较低的摩擦因数,平均摩擦因数为0.124,磨损率为2.17×10^(-3) mm 3·N^(-1)·m^(-1)。     

Thermodynamic properties of liquid Ga-Si-Mn alloys

The partial enthalpies of mixing of the constituent components (Δ_mix \(\bar H_i \)) have been determined by high-temperature calorimetry and then used to evaluate the integral enthalpies of mixing (Δ_mix H) of Ga-Si-Mn alloys along three cuts at 1770 ± 5 K. The results demonstrate that, in the composition region studied, the formation of Ga-Si-Mn alloys is an exothermic process. Δ_mix H is calculated over the entire composition region by the Bonnier-Caboz method.     

Volumetric and thermodynamic properties of liquid 2-fluoroethanol

p-V T data for liquid 2-fluoroethanol (FE) have been obtained in the form of volume ratios at six temperatures (278.15, 288.15, 298.14, 313.14, 323.14, and 338.130 K) at pressures from atmospheric to 314 MPa or higher. Freezing pressures have also been measured in the temperature range from the normal freezing point to 288 K. Densities at atmospheric pressure in the same temperature range as that for thep V T data are also reported. Isothermal compressibilities, isobaric expansivities, changes in the isobaric heat capacity, and internal pressures have been calculated from the volumetric data. Representation of the volume ratios for FE, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, and ethanol by a form of the modified Tait equation shows that the effect of the progressive substitution of fluorine into ethanol cannot be represented by a simple correlation.     

Concentration dependence of the spectral emissivity of liquid binary metallic alloys

A review is given on the literature data on the concentration dependence or the emissivity of liquid binary metallic alloys (Ni-Fe, Ce-Cu, Ni-Cr, Ti-Al). Our measurements at the liquidus temperatures are presented for the systems Ni-V, Fe-V, and Fe-Nb and the pure components at=547 nm and=650 nm. All available results are interpolated in comparison to the phase diagrams of the systems. This comparison indicates that the nonvariant liquidus temperatures have the highest deviation from a linear interpolation between the emissivity of the pure components. The corresponding concentration ranges are characterized by stronger atomic interactions in the melt. Therefore errors in noncontact temperature measurements occur if the concentration dependence is neglected or estimated from the pure components.     

Thermodynamic properties of liquid metals and alloys

A modified cellular model of liquids is used to develop a method for calculating thermodynamic properties of liquid metals and their alloys, which are widely used in compact modern heat exchange equipment operating at high thermal flux densities. The approach presented herein permits calculation of the properties of metals from various groups by a single consistent technique. Good agreement was found with experimental data for a significant number of liquid metals and their alloys.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 5, pp. 832–840, November, 1990.     

Validation of an effective oxidation pressure model for liquid binary alloys

Dynamic surface-tension measurements using the sessile drop method and acquisition times of a few seconds make it possible to study the evolution of the surface of molten metals and alloys and so reliably validate the predictive models of the interactions between pure liquid metals and an oxidizing atmosphere, in both an inert gas carrier and in a vacuum. The presence of active oxidation contributes to maintaining surface cleanness and then strongly affects the shape of the boundary separating oxidation and de-oxidation regimes. Recently the general physical–mathematical analysis we developed for pure liquid metals has been extended to liquid binary alloys and their oxides. In this work we present the experimental results of tests on some binary alloys chosen as test systems to try to obtain a preliminary validation of the extended model. The theoretical results obtained, indicating that the behaviour of the alloy towards oxidation tends to be similar to that of the less oxidizable component, have thus been confirmed experimentally.     

Viscosity of Al–Cu liquid alloys: measurement and thermodynamic description

In the present work a high temperature oscillating cup viscometer has been used to measure the viscosities of liquid binary Al–Cu alloys. The dependence of viscosity on temperature is well described by the Arrhenius law. For constant temperature, the viscosity as a function of copper concentration exhibits a maximum at a mole fraction x _Cu = 0.7. This might be due to a pronounced chemical short range order in the liquid phase at this composition. As the comparison of existing phenomenological models describing viscosity as a function of composition to the experimental data is unsatisfactory, a new model for the viscosity has been developed within this work based only on a few assumptions and using the enthalpy of mixing as input parameter which is easily accessible. The agreement between model calculation and experimental data is excellent.