Wetting Phenomena in bcc Binary Alloys

We study the influence of the surface orientation on the wetting behavior of bcc binary alloys, using a semiinfinite lattice model equivalent to a nearest-neighbor Ising antiferromagnet in an external magnetic field. This model describes alloys that exhibit a continuous B2–A2 order–disorder transition, such as FeAl or FeCo. For symmetry-breaking surfaces like (100), an effective ordering surface field g ₁0 emerges. Such a field not only crucially affects the surface critical behavior at bulk criticality, but also gives rise to wetting transitions below the critical temperature T _c. Starting from the mean-field theory for the lattice model and making a continuum approximation, a suitable Ginzburg–Landau model is derived. Explicit results for the dependence of its parameters (e.g., of g ₁) on the microscopic interaction constants are obtained. Utilizing these in conjunction with Landau theory, the wetting phase diagram is calculated.     

Liquid–Liquid–Vapor Equilibria in Binary Families of SF6, CClF3, C2H3F3, and C2H4 with n-Alkanes

Liquid–liquid–vapor equilibria were determined experimentally for binary and quasi-binary systems which consisted of a low-volatile n-alkane or mixture of n-alkanes with a more volatile component, chlorotrifluoromethane, sulfur hexafluoride, 1,1,1-trifluoroethane, and ethene. From the location of the critical end-points L ₂ = L ₁ + V and L ₂ + L ₁ = V of the three-phase curves, the coordinates of the tricritical point and the double critical endpoint of these families were estimated by extrapolation. For the families studied it was found that increasing the carbon number of the n-alkane leads to a transition from type II to type IV to type III fluid phase behavior.     

Thermophysical Properties of Undercooled Liquid Cu–Ni Alloys

Experimental data for the surface tension, density, and electrical resistivity of undercooled liquid Cu–Ni alloys of different compositions and at different temperatures are presented. The experiments were performed in facilities that combine the containerless positioning method of electromagnetic levitation with contactless measurement techniques. Although Cu–Ni alloys are rather simple from a chemical point of view, the data for density, surface tension, and electrical resistivity unveil the occurrence of short-range atomic order processes in the melt. For the density this manifests in a composition-dependent excess volume, for the surface tension in smaller values due to an increased surface segregation, and for the electrical resistivity in a deviation from the linear temperature dependence at low temperatures.     

二元互不溶体系中第二相颗粒的Ostwald熟化

二元互不溶体系是具有重要工程技术价值的材料。综述了近年来二元互不溶体系中第二相颗粒的Ostwald熟化的研究进展,简述了Ostwald熟化的经典理论——LSW理论和现代Ostwald熟化理论,着重介绍了二元互不溶体系中第二相颗粒的Ostwald熟化以及第二相体积分数、颗粒形状和合金元素的影响。     

Electrical Resistivity of Undercooled Liquid Cu-Ni Alloys

Measured values for the electrical resistivity of undercooled liquid Cu-Ni alloys of different compositions are presented. The experiments were performed in a facility that combines the containerless positioning method of electromagnetic levitation with the contactless inductive resistivity measurement technique. For high nickel concentrations, i.e., for the liquid Cu₂₀Ni₈₀ and Cu₄₀Ni₆₀ alloys, the electrical resistivity shows, as well as for pure nickel and pure copper, the typical linear temperature dependence in the whole range from above to below the liquidus temperature. A significant deviation from the linear behavior occurs for liquid Cu₆₀Ni₄₀ and, less distinct, also for liquid Cu₈₀Ni₂₀. This is explained by a formation of nickel associates in the melt that influence the scattering cross section of the conduction electrons.     

Reference Microgravity Measurements of Liquid Phase Solute Diffusivities in Tin- and Aluminum-Based Alloys

This paper presents results of the measurement of solute diffusivities in the Al–Ni and Sn–Bi–In systems. These experiments were conducted in microgravity and may therefore be assigned as reference values. A dedicated facility, which can be used for processing of four identical samples in parallel, was developed for the experiments under consideration. In addition, a rather thorough analysis of possible error sources in shear cell type experiments is carried out. Comparison with work carried out using magnetic fields to control convective flows, and with previous indirect measurements results, is also provided. A coherent picture emerges from the overall agreement between various measurements, and the data from the current work can thus be considered as reference benchmarks for future experiments. Another conclusion of the present study is that the shear cell technique is well suited for the measurement of solute diffusivities.     

Dual Critical Points and Related Phenomena in Simple Fluids from the Perspective of (Approximate) Renormalization Theory

It is known that some single component fluids can have coexisting low-density and high-density liquid phases with two, separate, gas–liquid and liquid–liquid, critical points. Such behavior is found both by experiments and in recent molecular-dynamics simulations performed for certain simple isotropic attractive pair potentials with softened repulsive cores. In the present investigation, a global renormalization group theory that was employed previously to make predictions for simple Lennard–Jones and square-well fluids over wide ranges of density and temperature, including the critical point, in reasonably good agreement with molecular dynamics and Monte Carlo simulations, is applied to simple shoulder potentials and to square-well potentials with softened repulsive cores. Results using this renormalization approach are compared with some previously reported results for a shoulder potential and expectations regarding dual critical points for water.     

Vapor–Liquid Equilibrium Measurements for Binary Mixtures Containing 1,1,1,2,3,3,3-Heptafluoropropane (HFC-227ea)1

Isothermal vapor–liquid equilibrium data for two binary mixtures of alternative refrigerants were determined by using an apparatus applying recirculating vapor and liquid. The difluoromethane (HFC-32)+1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and 1,1,1,2-tetrafluoroethane (HFC-134a)+1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) systems were studied at 298.15 and 312.65 K. The pressure and vapor and liquid compositions were measured at each temperature. The experimental data were correlated with the Peng–Robinson equation of state using the van der Waals one-fluid mixing rule. Calculated results show that this equation yields good agreement with the experimental data.     

ChCl-urea-NiCl_2-FeCl_3离子液体电沉积Ni-Fe合金

以ChCl-urea-NiCl2-FeCl3离子液体为电解质在Fe基体上电沉积得到了Ni-Fe合金镀层。循环伏安测试表明电沉积过程中由于金属Ni的生成诱导金属Fe发生欠电位沉积,从而实现了Ni-Fe合金的共沉积。同时研究了电流密度对镀层成分、形貌和耐蚀性能的影响,结果表明:电流密度由2mA/cm2增加到5mA/cm2时,合金镀层中Fe含量从10.74at%升高到39.21at%。当Fe含量为24.89at%时,镀层最为平整致密,耐蚀性能最好。此外,镀层的组成主要为FeNi3固溶体和Ni,还存在FeNi和Fe0.64Ni0.36合金相。     

Melting Enthalpy and Entropy of Binary Systems of Alloys of 3d Transition VII and VIII Metals and Carbon: Thermodynamic Calculation and Experimental Study

Thermodynamic calculations have been performed of the melting enthalpy and entropy of the Co–C, Ni–C, and Fe–C binary system alloys having eutectic compositions and of alloys whose compositions correspond to the minimum temperatures of the Mn–C, Fe–Co, Fe–Ni, and Mn–Ni melting diagrams. Heat capacities of one- and two-phase alloys of investigated systems have also been calculated as a function of temperature. In order to express a dependence of the Gibbs energy (G) of the liquid phase on the composition, the model of regular solutions has been used. The relation between the G of interstitial solid solutions and concentration was described by the two-sublattice model. The values have been experimentally verified using a high temperature calorimeter. These results have shown that the discrepancy between experimental and calculated results is within the calorimetric measurement uncertainty and does not exceed 10%.     

Controlling the Morphology of PVDF Hollow Fiber Membranes by Promotion of Liquid–Liquid Phase Separation

In literature, liquid–liquid (L–L) phase separation has been widely adopted as the principle technique by which polymeric membranes are produced. However, the promotion of L–L phase separation as the means of controlling membrane morphology is still debatable. Thus, this work aims to introduce a facile and cost‐effective technique for controlling the morphology of poly(vinylidene fluoride) (PVDF) hollow fiber membranes (HFMs). The proposed technique is based on promotion of L–L phase separation which can be achieved through two different approaches: 1) reducing the distance between locations of dope and binodal curve through locating spinning dope on nonsolvent (water)/solvent (2‐pyrrolidone)/polymer (PVDF) ternary phase diagram by increasing of nonsolvent content and maintaining of polymer concentration at initial level; 2) simultaneous occurrence of thermally and nonsolvent induced phase separation (TNIPS). It is found that L–L phase separation promotion based on the above described approaches yields to PVDF HFM with partially double‐layered structure, enhanced mechanical properties, higher porosity, and smaller average pore radius with the potential to purify textile wastewater containing C.I. Disperse Violet 33. The proposed technique is advantageous due to lack of need for additives or post‐treatment process for HFM synthesis.

     

Experimental Results on Tungsten-Wire Explosions in Air at Atmospheric Pressure—Comparison with a One-Dimensional Numerical Model

Experimental results on exploding tungsten wires in air at atmospheric pressure at current densities 10⁷ A·cm^–2 and a current rise 10¹⁰ A·s^–1 are presented. Besides the current through the probe and the voltage across it, the diameter of the wire material and its surface temperature have been measured. The final aim of this investigation is the determination of the thermophysical properties of a high-melting liquid metal up to its critical point. Here a first step should be made to demonstrate the reliability of the method and to justify the crucial assumptions. To determine the limits for the applicability of a homogeneous approach used so far, a one-dimensional numerical model in Z-pinch geometry has been used which gives the time evolution of the profiles of temperature, density, and pressure across the wire. The model describes well the main features observed in these experiments. A physical explanation for the maximum in the time dependences of the surface temperature is proposed. This behavior is related to special thermodynamic properties of a two-phase (liquid–gas) mixture forming in a peripheral layer around the liquid metal. The temperature limit is determined for which there are no remarkable gradients of temperature and density across the wire. The specific heat, the thermal expansion coefficient, and the electrical as well as thermal conductivity of liquid tungsten can now, in principle, be obtained. The parameters of the critical point of the liquid-vapor phase transition can also be estimated.     

Thermophysical Properties of W–Re Alloys Above the Melting Region

In earlier experiments we have studied pure elements with a fast pulse heating technique to obtain thermophysical properties of the liquid state. We report here results for thermophysical properties such as specific heat and dependences among enthalpy, electrical resistivity, and temperature, for four W–Re alloys (3.95, 21.03, 23.84, and 30.82 at % of Re) in a wide temperature range covering solid and liquid states. Thermal conductivity is calculated using the Wiedemann–Franz law for the liquid alloy, as.well as data for thermal diffusivity for the beginning of the liquid phase. Additionally, data for the entire temperature range studied have been analyzed in comparison with those of the constituent elements, tungsten and rhenium, since both metals have been studied previously with the same experimental technique. Such information is of interest in the field of metallurgy since W–Re alloys of low Re content in the region of mutual component solubility in the solid state are widely used as thermocouple materials for the purposes of high-temperature thermometry.     

Vapor–Liquid Equilibria For The Binary Difluoromethane (R-32) + Propane (R-290) Mixture

The vapor–liquid equilibrium of the mixture composed of difluoromethane (R-32) and propane (R-290) was studied in the temperature range between 273.15 and 313.15 K. The experimental uncertainties of temperature, pressure, and composition measurements were estimated to be within ±10 mK, ±3 kPa, and ±0.4mol%, respectively. Comparisons between the present data and available experimental data were made using the Helmholtz free energy mixture model (HMM) adopted in the thermophysical properties program package, REFPROP 6.0, as a baseline. In addition, the existence of an azeotrope and the determination of new adjustable parameters for HMM for the R-32 + R-290 mixture are discussed.     

Application of High-Speed Laser Polarimetry to Noncontact Detection of Phase Transformations in Metals and Alloys at High Temperatures

A high-speed laser polarimetry technique, developed recently for the measurement of normal spectral emissivity of materials at high temperatures, was used to detect solid–solid and solid–liquid phase transformations in metals and alloys in millisecond-resolution pulse-heating experiments. Experiments were performed where normal spectral emissivity at 633 nm was measured simultaneously with surface radiance temperature, resistance, and/or voltage drop across the specimen. It was observed that a phase transformation, as indicated either by an arrest in the specimen radiance temperature or changes in the resistance and/or voltage drop, generally caused a change in normal spectral emissivity. Experiments were conducted on cobalt, iron, hafnium, titanium, and zirconium to detect solid–solid phase transformations. Similar experiments were also performed on niobium, titanium, and the alloy 85titanium–15molybdenum (mass%) to detect solid–liquid phase transformations (melting).     

大块非晶合金在过冷液相区微塑性成形的研究进展

综述了大块非晶合金在过冷液相区微塑性成形的工艺、成形性能评价及有限元技术应用方面的研究进展.指出应用大块非晶合金在过冷液相区粘性流变特性的微塑性成形技术及分析和优化成形工艺的有限元技术发展迅速.展望了过冷液相区微塑性成形技术的进一步研究对大块非晶合金在MEMS典型精细零件加工方面应用的巨大推动作用.     

Thermal Conductivity of Binary Refrigerant Mixtures of HFC-32/125 and HFC-32/134a in the Liquid Phase

The liquid thermal conductivity of mixtures of HFC-32/125 and HFC-32/134a was measured using the transient hot-wire apparatus in the temperature ranges from 213 to 293 K and from 193 to 313 K, respectively, in the pressure range from 2 to 30 MPa and with HFC-32 mass fractions of 0.249, 0.500, and 0.750 for each system. The uncertainty of the thermal conductivity was estimated to be ±0.7%. For practical applications, the thermal conductivity data for the two mixtures were represented by a polynomial in temperature, pressure, and mass fraction of HFC-32 with a standard deviation of 1.0%.     

Phase Stability, Kinetic Diagrams and Diffusion Path in High Temperature Oxidation of Binary Solid-Solution Alloys

The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams,which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.     

Effects of Cu on Microstructures,Mechanical, and Magnetic Properties of Fe–Ni–P Alloys Fabricated by Liquid Phase Sintering

The Fe–Ni–P–Cu alloys with different copper content (0, 0.5, 1, and 2 wt%) are fabricated by liquid phase sintering (LPS) at 950 °C. The nano‐Cu powder is mechanically mixed for 90 min with Fe–Ni–P composite powder using the ethanol as the medium. The microstructure, microhardness and compressive properties of Fe–Ni–P–Cu alloys are investigated. The results indicate that the copper is beneficial to improve the mechanical properties of sintered specimens. The sample contains a small amount of γ‐(Fe, Ni) phase when the copper content is 1 wt%, which results in its the highest compressive yield strength (948.1 MPa). The highest microhardness of 371 HV is accessible in Fe–Ni–P–Cu alloy with 2 wt% Cu. The fracture surface analysis indicates that sintered specimens with Cu addition exhibit a typical intergranular mode.