Rob Brooks

Reference Data for the Density and Viscosity of Liquid Aluminum and Liquid Iron

The available experimental data for the density and viscosity of liquid aluminum and iron have been critically examined with the intention of establishing a density and a viscosity standard. All experimental data have been categorized into primary and secondary data according to the quality of measurement specified by a series of criteria. The proposed standard reference correlations for the density of the aluminum and iron are characterized by standard deviations of 0.65% and 0.77% at the 95% confidence level, respectively. The overall uncertainty in the absolute values of the density is estimated to be one of ±0.7% for aluminum and 0.8% for iron, which is worse than that of the most optimistic claims but recognizes the unexplained discrepancies between different methods. The standard reference correlations for the viscosity of aluminum and iron are characterized by standard deviations of 13.7% and 5.7% at the 95% confidence level, respectively. The uncertainty in the absolute values of the viscosity of the two metals is thought to be no larger than the scatter between measurements made with different techniques and so can be said to be ±14% in the case of aluminum and ±6% in the case of iron.

The physical properties of alloys in the liquid and “mushy” states

Data on the physical properties of alloys at high temperatures are urgently needed for the mathematical modeling of high-temperature processes such as casting, welding, secondary refining, dip melting, spray forming, and metal powder production. Data are required for those properties which are involved in heat and fluid flow in high-temperature processes. Levitated drop methods have been adopted to measure the surface tensions, densities, and enthalpies of commercial alloys, and rapid, transient methods have been developed to measure thermal conductivities to avoid the problem of convection. The results obtained for the properties of commercial alloys for the liquid and “mushy” states are discussed.

Viscosity measurement of liquid ternary Cu–Ni–Fe alloys by an oscillating cup viscometer and comparison with models

Abstract Viscosity data on Cu – Ni – Fe have been obtained using an oscillating cup viscometer. In this method, a liquid sample is suspended in a crucible which performs damped angular oscillations. Viscosities are calculated from the time period and the decay of the amplitude. The temperature dependence of the measured viscosities can be described by an exponential Arrhenius law, taking into account an activation energy for the viscous flow. The activation energies for the ternary alloys were found to be linear combinations of the corresponding activation energies of the pure elements Cu, Ni, and Fe. At constant temperature, a non ideal mixing behaviour was observed and the data were compared with several quantitative models. Close agreement of the experimental results was found with the predictions of two models by Kaptay and Hirai.

Physical property measurements for the mathematical modeling of fluid flow in solidification processes

Measurement methods are being developed to provide values for the density, viscosity, heat capacity, enthalpy, fraction solid, surface tension, and thermal diffusivity and conductivity of commercial alloys in the liquid and mushy states. These data are needed for the mathematical modeling of heat and fluid flow in solidification processes. This paper briefly describes the present state of development of apparatus for the measurement of density by the levitated drop and hydrostatic probe methods and viscosity by the oscillating viscometer in our laboratory.

Surface tension and viscosity of industrial alloys from parabolic flight experiments — Results of theThermoLab project

The surface tension and the viscosity of a series of industrial alloys have been measured by the oscillating drop technique with an electromagnetic levitation device under reduced gravity conditions in several parabolic flights. It was demonstrated that the 20 seconds of reduced gravity available in a parabola were sufficient for melting, heating into the liquid phase, and cooling to solidification of typically 7 mm diameter metallic specimen. The surface tension and the viscosity were obtained from the frequency and the damping time constant of the oscillation which were evaluated from the temperature signal of a highresolution pyrometer. Alloys processed included steels, Ni-based superalloys, and Ti-alloys which were supplied by industrial partners to the project. Three to four parabolas were sufficient to obtain the surface tension and the viscosity over a large range in temperature.

Thermophysical properties of slags for process control

Abstract Thermophysical properties have been shown to be important in a number of industrial processes. Unfortunately, for a number of properties there are scant data available and/or the data that are available are of dubious quality. In the Thermo-Physical Property Group at the National Physical Laboratory (NPL) the aim has been to develop measurement techniques capable of working in the difficult environments that are typical of industrial processes. This paper presents current developments at NPL in techniques to measure the thermal diffusivity of liquid slags using a laser flash and insights into the copper smelting process using interfacial tension techniques.

Thermophysical property measurements of high-temperature liquid metallic alloys - State of the art

In this report, a survey is presented about state-of-the-art thermophysical property measurements of liquid metallic: alloys at high temperatures. Methods for measuring both caloric quantities, like specific heat and thermal conductivity, and thermophysical properties, like density, surface tension and viscosity, are described in detail. Measurement techniques discussed include container-based as well as containerless techniques. Strengths and potential pitfalls in applying these methods are pointed out and recommendations for best-practice are given.

Observations of the Effects of Oxide Skins on the Oscillations of Electromagnetically Levitated Metal Droplets

AbstractThe surface tensions of liquid metals can be derived from measurements of the natural oscillation frequencies of levitated drops through the Rayleigh relation,

Thermodynamic Properties of CMSX-4 Superalloy: Results from the ThermoLab Project

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