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Irradiation-Induced Microstructural Changes in Alloy X-750

Published online by Cambridge University Press:  02 July 2020

E.A. Kenik*
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN37831-6376
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Extract

Alloy X-750 is a γ´-strengthened Ni-base alloy that is often used in nuclear power systems for its excellent corrosion resistance and good mechanical properties. However, radiation-induced segregation (RIS) and irradiation-assisted stress corrosion cracking (IASCC) can occur under neutron irradiation. The present study examines the microstructure and composition profiles in a heat of Alloy X-750 before and after neutron irradiation.

The material was in the HTH commercial heat treatment (lh at 1121°C + air cooling + 20h at 704°C). Specimens were prepared from both control material and material irradiated at 360°C to a fluence of 2.3 × 1020 n/cm2 (E > 1 MeV), which was estimated to produce -0.4 displacements per atom. High spatial resolution analytical electron microscopy was performed in a Philips EM400T/FEG operated in the STEM mode with a probe diameter of ∼1.4 nm (FWHM). Composition profiles were acquired in two different ways: all energy dispersive X-ray spectrometry (EDS) and some parallel-detection electron energy-loss spectrometry (PEELS) profiles were acquired as individual spot analyses, whereas the majority of the PEELS profiles were acquired as spectrum lines with ∼10 s acquisition times per point. The quoted compositions are as measured (wt%); no deconvolution for the effect of the excited volume was performed.

Type
Segregation and Diffusion Analysis in Materials
Copyright
Copyright © Microscopy Society of America 1997

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References

1.Mcllree, A.R., in Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors (NACE, Houston,TX 1984), 838.Google Scholar
2.Bajaj, R., Mills, W.J., Lebo, M.R., Hyatt, B.Z., and Burke, M.G., in Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors (NACE, Houston, TX 1995)1093.Google Scholar
3.Kenik, E.A., in Microstructure Evolution During Irradiation, 1996 MRS Symposia Proceedings, Materials Research Society, Pittsburgh (In Press).Google Scholar
4. Research at Oak Ridge National Laboratory SHaRE User Facility supported in part by Division of Materials Sciences, U.S. Department of Energy under contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation.Google Scholar