Effect of oxygen absorption on lattice parameter and specimen dilation in a tantalum-base alloy containing 8 pct tungsten and 2 pct hafnium. [1000/sup 0/C]
Journal Article
·
· Metall. Trans., A; (United States)
Sheet and tube specimens of a tantalum-base alloy containing 8% tungsten and 2% hafnium (T-111) were exposed to low pressure oxygen at 1000/sup 0/C to study the effect of oxygen absorption on lattice parameter and specimen dilation. Oxygen absorption produced an increase in weight and dilation which was proportional to exposure time at 1000/sup 0/C. In the as-doped condition, dilation is roughly equal to the lattice expansion, suggesting that the absorbed oxygen is retained mainly in the bcc base solution. After isothermal aging at 1400/sup 0/C, the lattice parameter of the as-doped specimen decreases sharply due to the precipitation of HfO/sub 2/ particles; however, the dilation is not affected. The solubility of oxygen in T-111 is calculated to be 64 ppm at 1400/sup 0/C, based on some thermodynamic considerations and lattice parameter measurements. The T-111 specimen dilated 1% after only an 80 h exposure at 1000/sup 0/C at an oxygen pressure of 1.3 x 10/sup -3/ Pa (1 x 10/sup -5/ torr). Comparison of creep rates in high vacuum with the dilation rate indicates that specimen dilation due to oxygen absorption is the main reason that causes a higher ''creep rate'' of refractory alloys in contaminated environments, especially under the conditions of high test temperature and low applied stress.
- Research Organization:
- Oak Ridge National Lab., TN
- OSTI ID:
- 6216896
- Journal Information:
- Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 9:7; ISSN MTTAB
- Country of Publication:
- United States
- Language:
- English
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36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
42 ENGINEERING
425002 -- Engineering-- Power Cycles-- Rankine-- (1980-)
AGING
ALLOYS
CREEP
CRYOGENIC FLUIDS
CRYSTAL STRUCTURE
DIFFUSION
DIRECT ENERGY CONVERTERS
ELEMENTS
FLUIDS
HEAT SOURCES
LATTICE PARAMETERS
LIQUID METALS
LIQUIDS
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NONMETALS
OXYGEN
PERMEABILITY
RADIOISOTOPE GENERATORS
RANKINE CYCLE POWER SYSTEMS
SOLUBILITY
SORPTION
TANTALUM ALLOY-T111
TANTALUM ALLOYS
TANTALUM BASE ALLOYS
THERMOELECTRIC GENERATORS
VERY HIGH TEMPERATURE
070300 -- Isotopic Power Supplies
30 DIRECT ENERGY CONVERSION
300303 -- Thermoelectric Generators-- Materials
Components
& Auxiliaries
36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
42 ENGINEERING
425002 -- Engineering-- Power Cycles-- Rankine-- (1980-)
AGING
ALLOYS
CREEP
CRYOGENIC FLUIDS
CRYSTAL STRUCTURE
DIFFUSION
DIRECT ENERGY CONVERTERS
ELEMENTS
FLUIDS
HEAT SOURCES
LATTICE PARAMETERS
LIQUID METALS
LIQUIDS
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NONMETALS
OXYGEN
PERMEABILITY
RADIOISOTOPE GENERATORS
RANKINE CYCLE POWER SYSTEMS
SOLUBILITY
SORPTION
TANTALUM ALLOY-T111
TANTALUM ALLOYS
TANTALUM BASE ALLOYS
THERMOELECTRIC GENERATORS
VERY HIGH TEMPERATURE