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An investigation of diffusion-mediated cyclic coarsening and reversal coarsening in an advanced Ni-based superalloy

Chen, Yiqiang, babu, R. Prasath, Slater, Thomas J.A., Bai, Mingwen, Mitchell, Robert, Ciuca, Octav, Preuss, Michael and Haigh, Sarah J. 2016. An investigation of diffusion-mediated cyclic coarsening and reversal coarsening in an advanced Ni-based superalloy. Acta Materialia 110 , pp. 295-305. 10.1016/j.actamat.2016.02.067

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Abstract

The anomalous cyclic coarsening behaviour of γ′ precipitates after ageing at 1073 K has been investigated for the low misfit commercial powder metallurgy (PM) Ni-based superalloy RR1000. Using scanning transmission electron microscope (STEM) imaging combined with absorption-corrected energy-dispersive X-ray (EDX) spectroscopy, the elemental segregation as a function of coarsening behaviour has been experimentally observed for secondary γ′ precipitates. Elemental EDX spectrum imaging has revealed nanoscale enrichment of Co and Cr and a depletion of Al and Ti within the γ matrix close to the γ-γʹ interface. Our experimental results, coupled with complementary modelling and synchrotron X-ray diffraction analysis, demonstrate the importance of elastic strain energy resulting from local compositional variations for influencing precipitate morphology. In particular, elemental inhomogeneities, as a result of complex diffusive interactions within both matrix and precipitates, play a crucial role in determining the rate of coarsening. Our findings provide important new evidence for understanding the microstructural evolution observed for advanced superalloys when they are exposed to different heat treatment regimes.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Publisher: Elsevier
ISSN: 1359-6454
Date of First Compliant Deposit: 24 February 2022
Date of Acceptance: 28 February 2016
Last Modified: 24 Feb 2022 09:45
URI: https://orca.cardiff.ac.uk/id/eprint/147175

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