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Lattice misfit during ageing of a polycrystalline nickel-base superalloy

DOI: 10.1016/j.actamat.2013.09.018 DOI Help

Authors: D Collins (University of Oxford) , L. Yan (University of Michigan) , E. A. Marquis (University of Michigan) , L Connor (Diamond Light Source) , J. J. Ciardiello (University of Cambridge) , A. D. Evans (Institut Laue-Langevin) , H. J. Stone (Rolls-Royce UTC)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Acta Materialia , VOL 61 , PAGES 7791 - 7804

State: Published (Approved)
Published: December 2013

Abstract: 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.

Journal Keywords: Misfit; Synchrotron radiation; X-ray diffraction (XRD); Coarsening; Heat Treatments; Lattice Parameters; Nickel; Nickel Alloys; Polycrystals; Synchrotron Radiation

Subject Areas: Materials

Technical Areas: