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Effects of grain and precipitate size variation on creep-fatigue behaviour of Udimet 720Li in both air and vacuum

Hide, N.J., Henderson, M.B. and Reed, P.A.S., (2000) Effects of grain and precipitate size variation on creep-fatigue behaviour of Udimet 720Li in both air and vacuum Green, K.A., Pollock, T.M. and Kissinger, R.D. (eds.) In Superalloys 2000: From the 9th International Symposium on Superalloys 2000, Champion, Pennsylvania, September 17-21 2000. Minerals, Metals and Materials Society. 9 pp, pp. 495-503.

Record type: Conference or Workshop Item (Paper)


The high temperature fatigue characteristics of U720Li have been investigated over the temperature range 650°C to 725°C under imposed dwell times (at maximum load) of 1 and 20 seconds in vacuum and air conditions. The effect of varying grain size and coherent precipitate size under these conditions has been assessed.
Testing in air resulted in oxidation dominated intergranular crack growth at all temperatures and dwell times with the slope (m-values) of the crack growth rate curves remaining constant. Increased crack growth rates are seen at the higher temperatures and at longer dwells, although no effect of dwell was observed at 650?C in the as-received fine grained variant. In vacuum crack growth rates were much lower than in air and a purely cyclic dependent regime was evident at 650°C. As temperature and dwell time at maximum load was increased, m-values increased and were accompanied by a change in crack growth mechanism from transgranular to intergranular cracking. This indicated that true, time-dependent, creep-fatigue processes were occurring.
The large grain variant of the U720Li showed little advantage in crack growth rates within the cyclic dependent and creep-fatigue regime, but did show a significant increase in resistance to crack growth in the time dependent (oxidation-fatigue) regime. The effect of the large precipitate variant was to give similar or worse crack growth resistance than the baseline U720Li at temperatures up to 725°C (1 second dwell) but improved crack growth resistance when oxidation processes predominated at 725°C in air with an imposed 20 second dwell.

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Published date: 2000
Venue - Dates: 9th International Symposium on Superalloys (Superalloys 2000), 2000-09-17 - 2000-09-21
Organisations: Engineering Mats & Surface Engineerg Gp


Local EPrints ID: 43046
ISBN: 0873395062
PURE UUID: d820d0de-34c3-4931-875b-5b90b2f80aa8
ORCID for P.A.S. Reed: ORCID iD

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Date deposited: 10 Jan 2007
Last modified: 17 Jul 2017 15:20

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Author: N.J. Hide
Author: M.B. Henderson
Author: P.A.S. Reed ORCID iD
Editor: K.A. Green
Editor: T.M. Pollock
Editor: R.D. Kissinger

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