Kinetic pathways for phase separation: An atomic-scale study in Ni-Al-Cr alloys

Zugang Mao, Christopher Booth-Morrison, Chantal K. Sudbrack, Georges Martin, David N. Seidman*

*Corresponding author for this work

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

The kinetic pathways involved in the formation of γ′(L1 2 structure)-precipitates during aging of concentrated Ni-Al-Cr alloys at 873 K, for three distinct alloy compositions, are studied experimentally by atom probe tomography, and computationally with lattice kinetic Monte Carlo (LKMC) simulations using parameters deduced from first-principles calculations of cohesive energies, and from experimental diffusion data. It is found that the compositional evolution of the γ′-precipitate phase does not follow the predictions of a classical mean-field model for coarsening of precipitates in ternary alloys. LKMC simulations reveal that long-range vacancy-solute binding plays a key role during the early stages of γ′-precipitation. With the aid of Monte Carlo techniques using the parameters employed in the LKMC simulations, we compute the diffusion matrix in the terminal solid-solutions and demonstrate that key features of the observed kinetic pathways are the result of kinetic couplings among the diffusional fluxes. The latter are controlled by the long-range vacancy-solute binding energies. It is concluded that, because it neglects flux couplings, the classical mean-field approach to phase separation for a ternary alloy, despite its many qualitatively correct predictions, fails to describe quantitatively the true kinetic pathways that lead to phase separation in concentrated metallic alloys.

Original languageEnglish (US)
Pages (from-to)1871-1888
Number of pages18
JournalActa Materialia
Volume60
Issue number4
DOIs
StatePublished - Feb 1 2012

Keywords

  • Atom probe tomography
  • Kinetic pathways
  • Lattice kinetic Monte Carlo
  • Nanostructures
  • Nickel-based superalloys

ASJC Scopus subject areas

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

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