Surface Tension, Viscosity, and Selected Thermophysical Properties of Ti48Al48Nb2Cr2, Ti46Al46Nb8, and Ti46Al46Ta8 from Microgravity Experiments
ADVANCED ENGINEERING MATERIALS(2018)
摘要
The surface tension and the viscosity of the alloys Ti48Al48Nb2Cr2, Ti46Al46Nb8, and Ti46Al46Ta8 are measured with the oscillating drop technique in an electromagnetic levitation device under reduced gravity conditions on board a parabolic flight airplane. The surface tensions as a function of temperature are obtained as sigma(T) = (1.19 +/- 0.02 - 3.80 x 10(-4) (T - 1856 K)) Nm(-1) for Ti46Al46Nb8, sigma(T) = (1.21 +/- 0.02 - 2.69 x 10(-4) (T - 1879 K)) Nm(-1) for Ti46Al46Ta8, and sigma(T) = (1.20 +/- 0.02 - 3.96 x 10(-4) (T - 1776 K)) Nm(-1) for Ti48Al48Nb2Cr2, concentrations in atomic per cent. The viscosities at the liquidus temperatures are obtained as eta(T-l) = 6.62 mPa(.)s, eta(T-l) = 6.9 mPa(.)s, and eta(T-l) = 5.8 mPa(.)s in the same order. All processed specimens are solidified at an undercooling of Delta T-u = 220 +/- 30 K. In addition, the solidus and liquidus temperatures and the enthalpies of fusion are determined by calorimetry. From the large undercooling and the enthalpy of fusion, the average specific heat capacity at an undercooling of 120 K is obtained as c(P)(av) = 1.30 +/- 0.20 J (kg)(-1) for all alloys. The thermal expansion between the room and solidus temperatures is measured by dilatometry.
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关键词
containerless processing,gamma titanium-aluminides,microgravity,oscillating drop method,surface tension and viscosity
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