Thermodynamic and kinetic studies of oxygen behavior in tantalum-based alloys

Technical Report · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5274139

Lee, J S

The experimental study of equilibrium and kinetic properties of oxygen in tantalum-based alloys was made by EMF measurements on solid electrolytic cells over the temperature range of 600 to 1100/sup 0/C. The terminal solubility of oxygen in tantalum was determined to be c/sub s/ = 12.4 exp (-(5.5 kJ/mole)/RT) over the experimental temperature range. It was concluded that oxygen obeys Henry's law for concentrations up to the terminal solubility in tantalum for the temperature range 600 to 1100/sup 0/C. The oxygen activity coefficient increased with Mo content in Ta-Mo alloys and decreased with V content in Ta-V alloys. The equilibrium results showed virtually no disturbance in thermodynamic behavior of oxygen solution by adding Nb to Ta-O alloys. The positive modifications of the oxygen activity coefficient in Ta-Mo alloys were believed to be due to repulsive interactions between molybdenum and oxygen atoms up to third nearest neighbors and probably to fourth or fifth nearest neighbor shells. The oxygen diffusion in tantalum was not significantly modified by small addition of Nb, V, Mo, Ni and Ti. The addition of W in tantalum had a larger effect in lowering oxygen diffusivity in Ta-W alloys. By alloying Ta with Cr, the oxygen diffusivity was lowered by more than an order of magnitude. Oriani's model was used to fit diffusion data in tantalum-based alloys and the values of trap energy were calculated. The binding energies, ..delta..E/sub X/, obtained from diffusion measurements in Ta-Nb-O alloys and Ta-V-O alloys were compared with the difference in nearest neighbor pairwise interaction energies epsilon/sub iu/ and epsilon/sub iv/ derived from equilibrium measurement on these two alloys, there was very good agreement between these two terms in Ta-Nb-O and Ta-V-O alloys. 113 references, 50 figures, 11 tables.

• Research Organization: Illinois Univ., Urbana (USA)
• DOE Contract Number: AC02-76ER01198
• OSTI ID: 5274139
• Report Number(s): DOE/ER/01198-1405; ON: DE84006487
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
ALLOYS
BINDING ENERGY
DATA
DIFFUSION
DISPERSIONS
ELECTROMOTIVE FORCE
ELEMENTS
ENERGY
ENTHALPY
ENTROPY
EQUILIBRIUM
EXPERIMENTAL DATA
HIGH TEMPERATURE
INFORMATION
KINETICS
METALS
MIXTURES
MOLYBDENUM ADDITIONS
MOLYBDENUM ALLOYS
NICKEL ADDITIONS
NICKEL ALLOYS
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
NONMETALS
NUMERICAL DATA
OXYGEN
PHYSICAL PROPERTIES
SOLID SOLUTIONS
SOLUBILITY
SOLUTIONS
TANTALUM
TANTALUM ALLOYS
TANTALUM BASE ALLOYS
THERMODYNAMIC PROPERTIES
TITANIUM ADDITIONS
TITANIUM ALLOYS
TRANSITION ELEMENTS
VANADIUM ADDITIONS
VANADIUM ALLOYS
VERY HIGH TEMPERATURE