Influence of cerium additions on high-temperature-impact ductility and fracture behavior of iridium alloys
- Auburn Univ., AL (United States)
- Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.
Radioisotope thermoelectric generators (RTGs), used for supplying electric power to interplanetary space missions, utilize the energy liberated due to decay of the radioisotope fuel. The material used for cladding the fuel pellets is an iridium-based alloy developed at Oak Ridge National Laboratory, which contains nominally 0.3 wt pct W, 60 wppm Th, and 50 wppm Al, generally known as DOP-26. High-temperature tensile impact testing was carried out on Ir + 0.3 wt pct W alloys doped with cerium and thorium individually, and with cerium and thorium together. Impact ductility was evaluated as a function of grain size and test temperature. Cerium by itself was not as effective as thorium in improving the grain boundary cohesion, even though it segregated more strongly than thorium to the grain boundaries. This lower grain boundary cohesion was responsible for lower impact ductility and higher brittle-to-ductile transition temperature of cerium-doped alloys compared to those of the thorium- or thorium plus cerium-doped alloys. Reduction in thorium content by a factor of 5 (from 50 to 10 appm) in the bulk did not result in any significant reduction in high-temperature impact ductility or an increase in the brittle-to-ductile transition temperature as long as sufficient cerium was added to provide grain refinement. Grain boundary strengths of thorium- and thorium plus cerium-doped alloys were almost identical.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 543479
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 10 Vol. 28; ISSN MMTAEB; ISSN 1073-5623
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
CERIUM
CHEMICAL COMPOSITION
DOPED MATERIALS
GRAIN BOUNDARIES
GRAIN SIZE
IMPACT STRENGTH
IRIDIUM ALLOYS
MICROSTRUCTURE
NESDPS Office of Nuclear Energy Space and Defense Power Systems
PRECIPITATION
TEMPERATURE DEPENDENCE
THERMOELECTRIC GENERATORS
THORIUM
TUNGSTEN ADDITIONS