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Thermophysical properties of the γ-TiAl alloy Ti-48Al-2Cr-2Ni in the liquid phase were investigated with a containerless electromagnetic processing device on board the International Space Station. Containerless processing is warranted by the high liquidus temperature T liq = 1 776 K and the high dissolution reactivity in the liquid phase. Thermophysical properties investigated include the surface tension and viscosity, density, specific heat capacity and the electrical resistivity. The experiments were supported by magnetohydrodynamic fluid flow calculations. The Ti-48Al-2Cr-2Ni alloy could be stably processed over extended times in the stable and undercooled liquid phase and exhibited an exceptional degree of undercooling before solidification. Experimental processes and thermophysical properties so obtained will be described. The experiments demonstrate the broad experimental capabilities of the electromagnetic processing facility on the International Space Station for thermophysical investigations in the liquid phase of metallic alloys not achievable by other methods.

The surface tension and the viscosity of the catalytic precursor alloys Ni-68.5 at.% Al, Ni-75 at.% Al and Ni-75 at.% Al-1.5 at.%. Cr were measured over a temperature range of about 400 K using the oscillating drop technique in an electromagnetic levitation device under reduced gravity conditions. The experiments were performed on board parabolic flights and on a TEXUS sounding rocket flight. At the liquidus temperatures of 1 604 K and 1398 K the viscosities of Ni-68.5 at.% Al and Ni-75 at.% Al were obtained as ν(Tliq) = 4.31 mPa · s and ν(Tliq) = 4.53 mPa · s, respectively. In the investigated temperature range the viscosity exhibited a linear temperature dependence. The surface tension as a function of temperature can be represented as ω(T) = 1.01 N m−1 – 2.8 · 10−4 (T – 1 603 K) N m−1 and ω(T) = 0.92 N m−1 – 1.40 · 10−4 (T – 1 398 K) N m−1 for Ni-68.5 at.% Al and Ni-75 at.% Al, respectively. Comparison of the experimental viscosities with predictions from different semi-empirical models showed that the latter underestimate the experimental values by between 25 and 40%.

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.