A correlative four-dimensional study of phase-separation at the subnanoscale to nanoscale of a Ni–Al alloy

Elizaveta Y. Plotnikov, Zugang Mao, Sung Il Baik, Mehmet Yildirim, Yongsheng Li, Daniel Cecchetti, Ronald D. Noebe, Georges Martin, David N. Seidman*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

8 Scopus citations


The temporal evolution of ordered γ′(L1 2 )-precipitates precipitating in a disordered γ(f.c.c.) matrix is studied in extensive detail for a Ni-12.5 Al at.% alloy aged at 823 K (550 °C), for times ranging from 0.08 to 4096 h. Three-dimensional atom-probe tomography (3-D APT) results are compared to monovacancy-mediated lattice-kinetic Monte Carlo (LKMC 1 ) simulations on a rigid lattice, which include monovacancy-solute binding energies through 4th nearest-neighbor distances, for the same mean composition and aging temperature. The temporal evolution of the measured values of the mean radius, 〈R(t)〉, number density, aluminum supersaturations, and volume fraction of the γ′(L1 2 )-precipitates are compared to the predictions of a modified version of the Lifshitz-Slyozov diffusion-limited coarsening model due to Calderon, Voorhees et al. The resulting experimental rate constants are used to calculate the Gibbs interfacial free-energy between the γ(f.c.c.)- and γ′(L1 2 )-phases, which enter the model, using data from two thermodynamic databases, and its value is compared to all exiting values. The diffusion coefficient for coarsening is calculated utilizing the same rate-constants and compared to all archival diffusivities, not determined from coarsening experiments, and it is demonstrated to be the inter-diffusivity, D˜, of Ni and Al. The monovacancy-mediated LKMC 1 simulation results are in good agreement with our 3-D APT data. The compositional interfacial width, for the {100}-interface, between the γ(f.c.c.)- and γ’(L1 2 )-phases, decreases continuously with increasing aging time and 〈R(t)〉, both for the 3-D APT results and the monovacancy-mediated LKMC 1 simulations, in disagreement with an ansatz intrinsic to the trans-interface diffusion-controlled coarsening model, which assumes the exact opposite trend for binary alloys.

Original languageEnglish (US)
Pages (from-to)306-333
Number of pages28
JournalActa Materialia
StatePublished - Jun 1 2019


  • Atom-probe tomography
  • Lifshit-Slyozov (LS) model
  • Monovacancy-mediated lattice kinetic Monte Carlo
  • Nickel-based superalloys
  • Temporal evolution

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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