Influence of cerium additions on high-temperature-impact ductility and fracture behavior of iridium alloys

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 i...

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Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 1997-10, Vol.28 (10), p.2049-2057
Main Authors: GUBBI, A. N, GEORGE, E. P, OHRINER, E. K, ZEE, R. H
Format: Article
Language:English
Subjects:
Applied sciences
Brittleness
Cerium
Cohesion
Cross-disciplinary physics: materials science
rheology
Ductile-brittle transition
Ductility
Ductility tests
Exact sciences and technology
Fatigue, corrosion fatigue, embrittlement, cracking, fracture and failure
Fatigue, embrittlement, and fracture
Grain boundaries
Grain refinement
Grain size
Heat resistant alloys
High temperature
Iridium base alloys
Materials science
Metals. Metallurgy
Physics
Reduction
Thorium
Transition temperature
Treatment of materials and its effects on microstructure and properties
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Summary: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 hightemperature 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.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-997-0161-z