Effects of tantalum on the temporal evolution of a model Ni-Al-Cr superalloy during phase decomposition

Christopher Booth-Morrison, Ronald D. Noebe, David N. Seidman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

The effects of a 2.0 at.% addition of Ta to a model Ni-10.0Al-8.5Cr (at.%) superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The γ′(L12)-precipitate morphology that develops as a result of γ-(fcc)matrix phase decomposition is found to evolve from a bimodal distribution of spheroidal precipitates, to {0 0 1}-faceted cuboids and parallelepipeds aligned along the elastically soft 〈0 0 1〉-type directions. The phase compositions and the widths of the γ′-precipitate/γ-matrix heterophase interfaces evolve temporally as the Ni-Al-Cr-Ta alloy undergoes quasi-stationary state coarsening after 1 h of aging. Tantalum is observed to partition preferentially to the γ′-precipitate phase, and suppresses the mobility of Ni in the γ-matrix sufficiently to cause an accumulation of Ni on the γ-matrix side of the γ′/γ interface. Additionally, computational modeling, employing Thermo-Calc, Dictra and PrecipiCalc, is employed to elucidate the kinetic pathways that lead to phase decomposition in this concentrated Ni-Al-Cr-Ta alloy.

Original languageEnglish (US)
Pages (from-to)909-920
Number of pages12
JournalActa Materialia
Volume57
Issue number3
DOIs
StatePublished - Feb 2009

Keywords

  • Atom-probe tomography
  • Nanostructures
  • Nickel-based superalloys
  • Tantalum

ASJC Scopus subject areas

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

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