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Surface Tension, Viscosity, and Selected Thermophysical Properties of Ti48Al48Nb2Cr2, Ti46Al46Nb8, and Ti46Al46Ta8 from Microgravity Experiments
Author(s) -
Wunderlich Rainer Karl,
Hecht Ulrike,
Hediger Fredy,
Fecht HansJörg
Publication year - 2018
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201800346
Subject(s) - liquidus , supercooling , solidus , materials science , enthalpy of fusion , thermodynamics , surface tension , calorimetry , enthalpy , analytical chemistry (journal) , viscosity , melting point , metallurgy , composite material , chemistry , physics , alloy , chromatography
The surface tension and the viscosity of the alloys Ti 48 Al 48 Nb 2 Cr 2 , Ti 46 Al 46 Nb 8 , and Ti 46 Al 46 Ta 8 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 σ ( T ) = (1.19 ± 0.02 − 3.80 × 10 −4 ( T − 1856 K)) Nm −1 for Ti 46 Al 46 Nb 8 , σ ( T ) = (1.21 ± 0.02 − 2.69 × 10 −4 ( T − 1879 K)) Nm −1 for Ti 46 Al 46 Ta 8 , and σ ( T ) = (1.20 ± 0.02 − 3.96 × 10 −4 ( T − 1776 K)) Nm −1 for Ti 48 Al 48 Nb 2 Cr 2 , concentrations in atomic per cent. The viscosities at the liquidus temperatures are obtained as η ( T l ) = 6.62 mPa . s, η ( T l ) = 6.9 mPa . s, and η ( T l ) = 5.8 mPa . s in the same order. All processed specimens are solidified at an undercooling of Δ 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.