Density and viscosity of ternary Al–Cu–Si liquid alloys

Densities and viscosities of ternary Al–Cu–Si liquid alloys have been investigated over a wide temperature and composition range. Density was measured using electromagnetic levitation as a container-less technique, while viscosity was measured by means of a high-temperature oscillating cup viscometer. In this ternary system, binary interaction parameters as well as a third (ternary) interaction parameter need to be taken into account for the excess volume to describe the liquid densities. The temperature dependences of the viscosities are well described by the Arrhenius law. A maximum of the activation energy of viscous flow is found in that compositional range in which intermetallic phases exist in the solid state.     

Viscosity Measurements of Industrial Alloys Using the Oscillating Cup Technique

Molten metal processing can be effectively simulated using state-of-the-art computer algorithms, and manufacturers increasingly rely upon these tools to optimize the design of their operations. Reliable thermophysical properties of the solid, solid + liquid, and liquid phases are essential for effective computer simulation. Commercially available instruments can measure many of the required properties of molten metals (e.g., transformation temperatures, thermal conductivity, specific heat, latent heat, and density). However, there are no commercially available instruments to characterize several important thermophysical properties (e.g., emissivity, electrical resistivity, surface tension, and viscosity). Although the literature has numerous examples of measurements of surface tension using the sessile drop and the oscillating drop techniques, literature references are sparse with regard to measurements of emissivity, electrical resistivity, and viscosity. The present paper discusses the development of an oscillating cup viscometer and its application to characterizing the viscosity of fully molten industrial alloys. The theory behind the oscillating cup technique is reviewed, and the design details of the current instrument are discussed. In addition, experimental data of the viscosity of several nickel-based superalloys are presented.     

A New High-Temperature Oscillating Cup Viscometer

A new oscillating cup viscometer for temperatures up to 2,300°C has been constructed. A vacuum furnace with a graphite heater is used for heating the sample. The temperatures of the furnace and sample are measured by both a thermocouple and a pyrometer. The temperature is controlled with a stability better than 1 K. The oscillation of the cup is measured with a reflected laser beam using a position sensitive detector. The measured values of angle and time are then fitted to an analytical oscillation function. From the parameters of this function, the viscosity values are calculated using the Roscoe formalism. Measurements were carried out on pure metals at temperatures up to 1,700°C because of limitations of the thermocouple. The obtained viscosity values showed good agreement with literature data.     

Viscosity of Industrially Important Al–Zn Alloys. I-Quasi-eutectic Alloys

Viscosity is a very important property in several fields of materials and metal processing. Many systems are still not fully characterized with regard to their thermophysical property data. In addition, as new alloys are developed or used, viscosity data are necessary to understand the best processing conditions. The data that are available frequently show large discrepancies. The effect of minor constituents is very difficult to model and can have a strong effect on the viscosity. Measurements of the viscosity of Zn–Al alloys, with a quasi-eutectic composition, were performed in the molten state, for temperatures between 690 K and 751 K. The measurements were performed with an oscillating cup viscometer, with an estimated uncertainty of 2 % to 5 %, depending on the alloy. The influence of other minor components, such as Pb, Mn, and Mg, on the viscosity of the alloys is discussed. It was concluded that Pb induces a decrease in viscosity, with Mg having the opposite effect, while the effect of Mn is not significant. All the alloys showed Newtonian behavior in the temperature range studied and a non-Arrhenius temperature dependence of viscosity, as usually found for pure molten metals.     

A High-Temperature Viscometer for Molten Materials

An oscillating-cup viscometer for the measurement of the viscosity of molten materials from room temperature to 1400 K was developed. The instrument is described in detail and the working equations are presented. The operational behavior was tested with water at room temperature. Preliminary measurements show that the new viscometer is capable of measuring the viscosity of water at room temperature to within 0.2%. As the primary objective of this work is the establishment of standard reference data for high-temperature viscosity measurements in molten salts, molten metals, and molten semiconductors, references of earlier viscosity measurements of molten KNO₃ are given.     

Density and viscosity of ternary Cr–Fe–Ni liquid alloys

The density and viscosity of ternary Cr–Fe–Ni liquid alloys have been investigated over a wide temperature range. The density was measured using electromagnetic levitation as a container-less technique, while viscosity was measured by means of a high-temperature oscillating cup viscometer. Although, the concentration dependence of density shows the influence of the second order (binary) interaction parameter in excess volume, the influence of a third order (ternary) interaction parameter in excess volume can be neglected. The temperature dependences of the viscosities are well described by the Arrhenius law. The viscosity increases monotonically as Fe or Cr concentration increases. For constant temperature, the viscosity as a function of iron molar faction can be described by a thermodynamic model using the enthalpy of mixing as input parameter.     

Viscosity of Molten Sodium Nitrate

New experimental data for the viscosity of molten sodium nitrate from its melting point up to 752 K, at atmospheric pressure, with an estimated uncertainty of 2.1%, were measured with an oscillating cup viscometer. A preliminary reference correlation and reference data are proposed, based on the best available data for the viscosity of molten sodium nitrate, for temperatures between 590 and 750 K, with an estimated absolute uncertainty of 0.066 mPa · s (k = 2).Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5-8, 2005, Bratislava, Slovak Republic.     

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.     

Viscosity of Molten GaSb and InSb

Viscosities of molten GaSb and InSb as III–V compound semiconductors were measured using an oscillating viscometer to study the thermophysical properties of semiconductor melts. A specially designed quartz crucible was used to prevent the evaporation of Sb from the melts. The measurements were performed in the temperature ranges from the melting point to about 1490 K for GaSb and from supercooled temperatures to about 1340 K for InSb. The viscosities obtained for both GaSb and InSb showed good Arrhenius linearity despite their wide temperature ranges. The activation energies of GaSb and InSb were almost the same, although the absolute viscosity of GaSb was slightly higher than that of InSb. It was concluded that most semiconductors including Si and Ge show Arrhenius behavior and have a low viscosity. The reason for the low viscosity is considered to be related to their melt structure, which may be similar to that of molten metals with low melting points.     

Viscosity of Industrially Important Zn–Al Alloys Part II: Alloys with Higher Contents of Al and Si

The viscosity of Zn–Al alloys melts, with industrial interest, was measured for temperatures between 693 K and 915 K, with an oscillating cup viscometer, and estimated expanded uncertainties between 3 and 5?%, depending on the alloy. The influence of minor components, such as Si, Mg and Ce?+?La, on the viscosity of the alloys is discussed. An increase in the amount of Mg triggers complex melt/solidification processes while the addition of Ce and La renders alloys viscosity almost temperature independent. Furthermore, increases in Al and Si contents decrease melts viscosity and lead to an Arrhenius type behavior. This paper complements a previous study describing the viscosity of Zn–Al alloys with quasi-eutectic compositions.     

Transversely Oscillating MEMS Viscometer: The “Spider”

The analysis of a new viscometer that takes the form of an oscillating plate, fabricated from silicon using the methods of micro-electro-mechanical-systems (MEMS) is considered. The instrument is designed principally for experimental use in the oil industry. The plate is 1.6 mm wide, 2.4 mm long, and 20μm thick. It is suspended from a 0.4 mm thick support by 48 square cross-section legs, each of length 0.5 mm width and depth of 20μm. The process of lithography is used to deposit layers atop the silicon. These layers can then be formed into resistors and metallic tracks. The tracks traverse the supporting legs to provide connections between the plate and external electronics. The oscillating plate is a mechanical element that can be set in motion by the force produced by the interaction between an electric current flowing in the plate and an externally applied magnetic field. The viscometer can be operated either in forced or transient mode and is intended for use in both Newtonian and non-Newtonian fluids. The motion of the viscometer is analyzed for incompressible fluids, using the Navier–Stokes equations to model the flow for both a Newtonian viscous fluid and a viscoelastic fluid where the stress is modeled by a reduced form of Maxwell’s equations.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Nanoliter viscometer for analyzing blood plasma and other liquid samples

We have developed a microfabricated nanoliter capillary viscometer that quickly, easily, and inexpensively measures the viscosity of liquids. The measurement of viscosity is based on capillary pressure-driven flow inside microfluidic channels (depth approximately 30 microm and width approximately 300 microm). Accurate and precise viscosity measurements can be made in less than 100 s while using only 600 nL of liquid sample. The silicon-glass hybrid device (18 mm by 15 mm) contains on-chip components that measure the driving capillary pressure difference and the relevant geometrical parameters; these components make the nanoliter viscometer completely self-calibrating, robust, and easy to use. Several different microfabricated viscometers were tested using solutions with viscosities ranging from 1 to 5 cP, a range relevant to biological fluids (urine, blood, blood plasma, etc.). Blood plasma samples collected from patients with the symptoms of hyperviscosity syndrome were tested on the nanoliter capillary viscometer to an accuracy of 3%. Such self-calibrating nanoliter viscometers may have widespread applications in chemical, biological, and medical laboratories as well as in personal health care.     

Investigation of Inner Vacuum Sucking method for degassing of molten aluminum

Hydrogen is a harmful gas element that is appreciably soluble in aluminum and its alloys. Removal of hydrogen from molten aluminum has been one of the most important tasks in aluminum melt processing. In this paper, a patented degassing process, which is based on principle of vacuum metallurgy, is proposed. A porous head that connects a vacuum system is immersed in the molten aluminum. The vacuum is created within the porous head and the dissolved hydrogen will diffuse unidirectionally towards the porous head according to Sievert's law. In this way, the hydrogen in the molten aluminum can be removed. The Fick's diffusion equation is used to explain hydrogen transfer in the molten aluminum. RPT experiments are carried out to evaluate the effectiveness of the new degassing process. The experiments indicate that the hydrogen content can be dramatically reduced by use of this process.     

Measurement and correlation of viscosity of HFC227ea and HFC236fa in the vapor phase

The viscosities of HFC227ea and HFC236fa in vapor phase were measured with an oscillating disk viscometer of the Maxwell type at the temperature range from 300 to 370 K and pressures up to 2.0 MPa. The uncertainty of the reported viscosities was estimated to be within ±2.0% with a coverage factor of k = 2. The experimental viscosities at 0.1 MPa were employed to determine the intermolecular potential parameters with the aid of the extended law of corresponding states developed by Kestin et al. In addition, viscosity models in the vapor phase based on the friction theory at high pressures were correlated for both HFC227ea and HFC236fa.     

A Perturbed Hard-Sphere Equation of State for Alkali Metal Alloys

A perturbed hard-sphere equation of state for liquid alkali metals has been employed to calculate the liquid density of alkali metal alloys over a wide range of temperature. Two temperature-dependent parameters appear in the equation of state, which are universal functions of the reduced temperature, i.e., two scale parameters are sufficient to calculate the temperature-dependent parameters, and hence, to predict the equation of state. In this article, calculated results of the liquid density of binary molten alloys of Na–K and K–Cs over the whole range of concentration at temperatures from the freezing point up to several hundred kelvin above the boiling point reproduce accurately the experimental PVT data points.     

Simultaneous Measurement of Viscosity and Density with an Oscillating-Disk Instrument: The Effect of Fixed Plates

The period and damping of the free motion of a body oscillating in a fluid depend on the fluid's viscosity and density. Commonly, a working equation which expresses the damping as a function of the viscosity and density is solved for the viscosity, the damping being measured and the density being treated as an independently supplied parameter. Another working equation exists for the period, and, in general, the period depends on a combination of the viscosity and the density which is linearly independent of the combination that appears in the damping equation. It is, therefore, in principle, possible to determine both the viscosity and the density by a simultaneous solution of the two coupled working equations, since the period also is measured. In this paper, the working equations that describe the oscillating-disk viscometer are reviewed and their simultaneous solution is considered. The effect of fixed plates symmetrically located above and below the oscillating disk is of specific interest. The paper's main result is that fixed plates can dramatically increase the independence of the damping and period working equations, so that it becomes indeed feasible to determine the viscosity and the density of a fluid simultaneously from the damping and period of oscillating motion. A price is paid, however, because the instrument's working equations when plates are present have multiple solutions. Under special conditions, these multiple solutions can coalesce, and then one can only deduce the viscosity from the damping equation if the density is known a priori.     

金属熔体电磁成形过程研究

以制备无污染的航空发动机叶片为背景 ,分析了金属熔体电磁成形定向凝固技术的原理 ,并以铝合金及 1Cr1 8Ni9Ti为研究材料 ,探讨了交流电磁场作用下金属熔体的感应加热熔化及约束成形过程 ,结果表明 :感应器结构决定其内部的磁场及电磁压力分布 ,感应器输入功率、熔体高度、上下液固界面位置、抽拉速度及冷却条件等参数综合影响金属加热熔化特性、熔体形状及其稳定性 ;通过控制合理的工艺参数 ,获得了截面为圆形及近似弯月面形、表面质量和内部定向组织良好的样件 .     

Perfect wettability of carbon by liquid aluminum achieved by a multifunctional flux

The wettability of carbon (graphite and glassy carbon) by liquid aluminum was studied. A special molten salt (flux) system was developed under which perfect wettability (a zero contact angle) of liquid aluminum was achieved on carbon surfaces. The principal component of the flux is K₂TiF₆ dissolved in a molten alkali chloride. K₂TiF₆ is a multifunctional flux component as it performs the following tasks: (i) dissolves the oxide layer covering liquid aluminum, (ii) through an exchange reaction with liquid aluminum it ensures the necessary amount of Ti dissolved in liquid Al, which is needed to cover the Al/C interface by TiC. As TiC is a metallic carbide, it is perfectly wetted by liquid Al–Ti alloys. In this paper, the conditions of perfect wettability of carbon by liquid Al under MCl–K₂TiF₆ molten salts (fluxes) are found as function of: (i) the basic component of the flux (MCl = LiCl, or NaCl–KCl or CsCl), (ii) K₂TiF₆ content of the flux, (iii) temperature, (iv) flux:Al weight ratio, (v) specific surface area of Al, and (vi) specific surface area of carbon. A simplified theoretical equation is derived to reproduce the experimental data.     

Liquid Viscosity of Binary Mixtures of Methanol with Ethanol and 1-Propanol from 273.15 to 333.15 K

The liquid viscosities and densities of two binary mixtures of methanol with ethanol and 1-propanol were measured in the temperature range from 273.15 to 333.15 K with a capillary viscometer and a glass pycnometer, respectively. The uncertainties in the measured viscosities were estimated to be smaller than 1.3%. The experimental viscosity values could be fitted to the Mertsch and Wolf equation within 2%.     

Measurements of the Liquid Viscosities of Mixtures of Isobutane with Squalane to 30 MPa

The viscosities of liquid mixtures of isobutane with squalane, which seem to be representative of mixtures of refrigerants with refrigeration oil, were measured from 273.15 to 333.15 K at pressures to 30 MPa using a falling-body viscometer. The uncertainty of the measurements was estimated to be no larger than 2.9%. The experimental viscosity values were fitted with a Tait-like equation within 2.8%. There are large deviations between the experimental data and calculated values predicted by the equation of Kanti et al., which is derived from Flory’s theory. By introducing two index numbers of the energetic mixing rule into the equation, the predictions could be improved considerably.