The effect of low-pressure oxygen exposure on the high-temperature tensile impact ductility of a thorium-doped iridium alloy

• Published in: Scripta materialia 1996-07, Vol.35 (2), p.181-185
• Main Authors: McKamey, C.G., Lee, E.H., Cohron, J.W., George, E.P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fatigue, corrosion fatigue, embrittlement, cracking, fracture and failure; Fatigue, embrittlement, and fracture; Materials science; Metals. Metallurgy; Physics; Treatment of materials and its effects on microstructure and properties
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/1359-6462(96)00119-4

High-temperature impact tests as a function of impact test temperature were conducted on Ir-0.3%W+60 wppm Th specimens which had been exposed to 1.3 mPa of oxygen for 3000 h at 1330 deg C. The impact ductility data were then compared to data from specimens that had been annealed in vacuum to produce comparable grain sizes. The results indicate that exposure to low-pressure oxygen embrittles this alloy, and that the embrittlement is due not only to an increase in the average grain size, but also to the loss of thorium from grain boundaries and the anomalous growth of near-surface grains. in this series of tests, the ductile-to-brittle transition temperature for new-process material was increased (for comparable average grain sizes) from approx1000 deg C in the unoxidized samples to 1200 deg C in the oxygen-annealed samples.