The effects of refractory elements on Ni-excesses and Ni-depletions at γ(f.c.c.)/γ′(L12) interfaces in model Ni-based superalloys: Atom-probe tomographic experiments and first-principles calculations

Yanyan Huang, Zugang Mao, Ronald D. Noebe, David N. Seidman*

*Corresponding author for this work

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

The effects of refractory (R) elements (R = Re, Ru, W, or Ta) on a base Ni-Al-Cr alloy are studied, for an aging temperature of 1073 K (800 °C) and an aging time of 256 h, employing atom-probe tomography (APT) and first-principles calculations. We find that there are strong attractive chemical binding energies between R-elements and solute (S) atoms (S = Al, Cr) in Ni-Al-Cr based alloys utilizing experimental partial radial distribution function (RDF) results, and first-principles calculations performed at 0 K. We demonstrate that correlated R-S binding energies play a key role in the observed Ni retention-excesses at γ(f.c.c.)/γ′(L12-structure) interfaces at aging times as long as 256 h. The total reduction of the γ(f.c.c.)/γ′(L12) interfacial energy, as a result of Ni interfacial-excesses in both γ(f.c.c.)-matrix and γ′(L12)-precipitates, lies between −0.16 ± 0.06 mJ m−2 and −0.05 ± 0.02 mJ m−2. The R-S binding energies cause changes in the compositional diffusion flux-vectors in and out of γ′(L12)-precipitates, which result in larger solvent Ni retention-excesses and wider interfacial compositional widths at 256 h, when compared with the base Ni-Al-Cr alloy. Refractory elements are slow diffusers in nickel and the attractive R-Cr binding energies decelerate the solute diffusional fluxes, which results in a decrease of the Ni diffusivity, which in turn hinders the flux of Ni atoms away from the γ(f.c.c.)/γ′(L12) interfaces.

Original languageEnglish (US)
Pages (from-to)288-298
Number of pages11
JournalActa Materialia
Volume121
DOIs
StatePublished - Dec 1 2016

Keywords

  • Atom-probe tomography
  • Binding energies
  • First-principles calculations
  • Interfacial excesses
  • Ni-based superalloys

ASJC Scopus subject areas

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

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