The influence of tungsten on the chemical composition of a temporally evolving nanostructure of a model Ni-Al-Cr superalloy

Chantal K. Sudbrack, Dieter Isheim, Ronald D. Noebe, Nathan S. Jacobson, David N. Seidman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

The influence of W on the temporal evolution of γ′ precipitation toward equilibrium in a model Ni-Al-Cr alloy is investigated by three-dimensional atom-probe (3DAP) microscopy and transmission electron microscopy (TEM). We report on the alloys Ni-10 Al-8.5 Cr (at.%) and Ni-10 Al-8.5 Cr-2 W (at.%), which were aged isothermally in the γ + γ′ two-phase field at 1073 K, for times ranging from 0.25 to 264 h. Spheroidal-shaped γ′ precipitates, 5-15 nm diameter, form during quenching from above the solvus temperature in both alloys at a high number density (∼1023 m-3). As γ′ precipitates grow with aging at 1073 K, a transition from spheriodal- to cuboidal-shaped precipitates is observed in both alloys. The elemental partitioning and spatially resolved concentration profiles across the γ′ precipitates are obtained as a function of aging time from three-dimensional atom-by-atom reconstructions. Proximity histogram concentration profiles (Hellman et al., 2000) of the quaternary alloy demonstrate that W concentration gradients exist in γ′ precipitates in the as-quenched and 0.25-h aging states, which disappear after 1 h of aging. The diffusion coefficient of W in γ′ is estimated to be 6.2 × 10-20 m2 s-1 at 1073 K. The W addition decreases the coarsening rate constant, and leads to stronger partitioning of Al to γ′ and Cr to γ.

Original languageEnglish (US)
Pages (from-to)355-365
Number of pages11
JournalMicroscopy and Microanalysis
Volume10
Issue number3
DOIs
StatePublished - Jun 2004

Keywords

  • Aluminum
  • Chromium
  • Coarsening
  • Decomposition
  • Nanostructure
  • Nickel-base superalloy
  • Partitioning ratio
  • Proxigram
  • Temporal evolution
  • Three-dimensional atom-probe microscopy
  • Tungsten

ASJC Scopus subject areas

  • Instrumentation

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