Lattice misfit during ageing of a polycrystalline nickel-base superalloy

The temporal evolution of the lattice parameters and lattice misfit of an advanced polycrystalline nickel-base superalloy have been studied in situ during an ageing heat treatment using synchrotron X-ray diffraction. During ageing, the γ and γ′ lattice parameters were both observed to decrease, a tr...

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Bibliographic Details
Published in:Acta materialia 2013-12, Vol.61 (20), p.7791-7804
Main Authors: Collins, D.M., Yan, L., Marquis, E.A., Connor, L.D., Ciardiello, J.J., Evans, A.D., Stone, H.J.
Format: Article
Language:English
Subjects:
Applied sciences
Coarsening
Exact sciences and technology
Metals. Metallurgy
Misfit
Nickel alloys
Synchrotron radiation
X-ray diffraction (XRD)
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Summary:The temporal evolution of the lattice parameters and lattice misfit of an advanced polycrystalline nickel-base superalloy have been studied in situ during an ageing heat treatment using synchrotron X-ray diffraction. During ageing, the γ and γ′ lattice parameters were both observed to decrease, a trend that cannot be attributed to a loss of coherency alone. Phase-extracted γ′ replicated this behaviour. Atom probe tomography was used to measure the compositional changes between the start and end of the ageing heat treatment. Using these data, a thermodynamic assessment was made using the software ThermoCalc of the structural change across the interface between γ and γ′. Subsequently, the unconstrained lattice parameters were estimated and were shown to be in good agreement with the X-ray diffraction measurements. Thus, the observed anomalous lattice misfit behaviour was concluded to be dominated by elemental exchange between the γ and γ′ phases during ageing.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2013.09.018