Thermophysical Properties of Al–Ti Binary Liquid Alloys

Thermophysical properties of liquid Co–Cr–Mo alloys measured by electromagnetic levitation in a static magnetic field

This study aimed to accurately measure the density (ρ), normal spectral emissivity (ε), heat capacity at constant pressure (Cp), and thermal conductivity (κ) of the Ti–6 mass % Al–4 mass % V (Ti64) melt by electromagnetic levitation with a static magnetic field and laser modulation calorimetry. A static magnetic field was applied to the levitated Ti64 melt to suppress the surface oscillation and translational motion of the droplets, and to suppress the convection flow inside the droplet for each property measurement, as needed. The measurement uncertainty was analyzed for all of the thermophysical property data. The excess volume and excess heat capacity of the Ti64 melt obtained in this study were compared with those evaluated using the ideal solution model. The contribution of the thermal vibrations of the atoms in κ for the Ti64 melt was evaluated from the difference between the measured thermal conductivity (κ) value and the κ values calculated using the Wiedemann–Franz law.

The normal spectral emissivity at 807 and 940 nm and heat capacity at constant pressure of Pd–Fe melts were measured under electromagnetic levitation with a static magnetic field. The samples were made of Fe of mass purity 99.9985%. The present emissivity of Fe melts was relatively low compared with previously reported data using Fe with purity lower than 99.95% mass purity. The spectral emission of the Fe melts was analyzed using their normal spectral emissivity obtained from the Drude model. The excess heat capacity of Pd–Fe melts was evaluated from the measured heat capacity of Pd–Fe melts. Applying the Lupis–Elliot rule, we concluded from the obtained excess heat capacity that the enthalpy of mixing and excess entropy of the Pd–Fe melts should be negative. The composition dependence of the enthalpy of mixing, excess entropy, and excess Gibbs energy of Pd–Fe melts were evaluated using data obtained in this study and the literature.

Pulse-heating experiments were performed on niobium strips, taking the specimens from room temperature to the melting point is less than one second. The normal spectral emissivity of the strips was measured by integrating sphere reflectometry, and, simultaneously, experimental data (radiance temperature, current, voltage drop) for thermophysical properties were collected with sub-millisecond time resolution. The normal spectral emissivity results were used to compute the true temperature of the niobium strips; the heat capacity, electrical resistivity, and hemispherical total emissivity were evaluated in the temperature range 1100 to 2700 K. The results are compared with literature data obtained in pulse-heating experiments. It is concluded that combined measurements of normal spectral emissivity and of thermophysical properties on strip specimens provide results of the same quality as obtained using tubular specimens with a blackbody. The thermophysical property results on niobium also validate the normal spectral emissivity measurements by integrating sphere reflectometry.

An electromagnetic levitation technique performed in a static magnetic field was used to measure density, surface tension, normal spectral emissivity, heat capacity, and thermal conductivity of molten 316L stainless steel (SS316L) and SS316L that contained 5 mass % B4C. The addition of 5 mass % B4C to the SS316L yielded reductions of 111 K, 6%, 19%, and 6% in the liquidus temperature, density, normal spectral emissivity, and thermal conductivity at the liquidus temperature of the SS316L, respectively. The heat capacity increased by 5% with this addition. Although the addition of 5 mass % B4C had no clear effect on the surface tensin, sulfur dissolved in the SS316L caused a significant decrease in the surface tension.

Normal spectral emissivity, specific heat capacity, and thermal conductivity of type 316 austenitic stainless steel containing up to 10 mass% B4C in a liquid state

It is very difficult to determine normal spectral emissivity under pulse‐heating conditions in the liquid state. Nevertheless normal spectral emissivity is an important quantity for temperature determination when measuring thermophysical properties. In the 80s Azzam [1] developed a laser polarimeter for the determination of optical parameters without any moving parts. Recently such a polarimeter was adapted for pulse‐heating experiments, which are performed in a sub‐microsecond time‐scale, and integrated into the existing measurement setup. The behavior of normal spectral emissivity for liquid metals at 684.5 nm can be illustrated by three groups: a) increasing, b) decreasing, or c) constant emissivity values as a function of temperature in the liquid phase. To achieve reliable thermophysical properties of liquid metals involves the measurement of normal spectral emissivity in conjunction with the radiometric temperature. Within this paper recent results of normal spectral emissivity at 684.5 nm as well as thermophysical properties for zirconium at melting and for the liquid phase are reported.

Thermophysical properties of Ni-Ti melts measured by electromagnetic levitation method using static magnetic field

Normal spectral emissivity characteristics of roughened cobalt and improved emissivity model based on Agababov roughness function

The normal spectral emissivity at 807 nm and molar heat capacity at constant pressure of Fe–Ni melts were successfully measured by the combination of an electromagnetic levitation technique and a static magnetic field. The static magnetic field suppressed the surface oscillation and translational motion of the levitated sample droplet to reduce the experimental uncertainty in the measurements. For all compositions of the melts, the normal spectral emissivity values and molar heat capacities showed negligible temperature dependence. The excess heat capacity of the melts was evaluated as a function of composition. This analysis showed a positive deviation from the Neumann–Kopp rule over the entire composition range. Moreover, enthalpy of mixing was calculated from the excess heat capacity up to 2200 K.

Polarimetric emissivity measurements adapted for a rapid pulse heating setup and recent results of normal spectral emissivity at 684.5 nm for molybdenum at melting and in the liquid phase are presented. Also reported is a complete set of thermophysical data (specific enthalpy, isobaric heat capacity, electrical resistivity, thermal conductivity, and thermal diffusivity) for molybdenum for both solid and liquid states. The results for all mentioned thermophysical properties are discussed and furthermore compared to literature values. The normal spectral emissivity and the electrical resistivity of molybdenum show opposite trends in the liquid phase, leading to the conclusion that a prediction of normal spectral emissivity at the given wavelength of 684.5 nm based on the Hagen–Rubens-relation and electrical resistivity measurements is not applicable.

Normal spectral emissivity study for GH3044 alloy and Ti-6Al-4V alloy

Effect of the surface oxidization and nitridation on the normal spectral emissivity of titanium alloys Ti–6Al–4V at 800–1100 K at a wavelength of 1.5 μm

In this study, we tried to develop a model to predict the effect of surface oxidization on the normal spectral emissivity of aluminum 5052 at a temperature range of 800 to 910 K and wavelength of \(1.5\,\upmu \hbox {m}\). In experiments, specimens were heated in air for 6 h at certain temperatures. Two platinum–rhodium thermocouples were symmetrically welded onto the front surface of the specimens near the measuring area for accurate monitoring of the temperature at the specimen surface. The temperatures measured by the two thermocouples had an uncertainty of 1 K. The normal spectral emissivity values were measured over the 6-h heating period at temperatures from 800 K to 910 K in increments of 10 K. Strong oscillations in the normal spectral emissivity were observed at each temperature. These oscillations were determined to form by the interference between the radiation stemming from the oxide layer and radiation from the substrate. The present measurements were compared with previous experimental results, and the variation in the normal spectral emissivity at given temperatures was evaluated. The uncertainty of the normal spectral emissivity caused only by the surface oxidization was found to be approximately 12.1 % to 21.8 %, and the corresponding uncertainty in the temperature caused only by the surface oxidization was approximately 9.1 K to 15.2 K. The model can reproduce the normal spectral emissivity well, including the strong oscillations that occur during the initial heating period.

The normal spectral emissivity of molten copper was determined in the wavelength range of 780–920 nm and in the temperature range of 1288–1678 K, by directly measuring the radiance emitted by an electromagnetically levitated molten copper droplet under a static magnetic field of 1.5 T. The spectrometer for radiance measurement was calibrated using the relation between the theoretical blackbody radiance from Planck's law and the light intensity of a quasi-blackbody radiation source measured using a spectrometer at a given temperature. As a result, the normal spectral emissivity of molten copper was determined as 0.075 ± 0.011 at a wavelength of 807 nm, and it was found that its temperature dependence is negligible in the entire measurement temperature range tested. In addition, the results of the normal spectral emissivity and its wavelength dependence were discussed, in comparison with those obtained using the Drude free-electron model.