The bi-layered precipitate phase ζ in the Al-Ag alloy system

Zezhong Zhang, Laure Bourgeois, Julian M. Rosalie, Nikhil V. Medhekar

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The Al-Ag system is thought to be a well-understood model system used to study diffusional phase transformations in alloys. Here we report the existence of a new precipitate phase, ζ, in this classical system using scanning transmission electron microscopy (STEM). The ζ phase has a modulated structure composed of alternating bilayers enriched in Al or Ag. Our in situ annealing experiments reveal that the ζ phase is an intermediate precipitate phase between GP zones and γ. First-principles calculations show that ζ is a local energy minimum state formed during Ag clustering in Al. The layered structure of ζ is analogous to the well-known Ag segregation at the precipitate-matrix interfaces when Ag is microalloyed in various aluminium alloys.

Original languageEnglish
Pages (from-to)525-537
Number of pages13
JournalActa Materialia
Publication statusPublished - 15 Jun 2017


  • Aluminium alloys
  • Atomic structure
  • Density functional theory (DFT) calculation
  • Precipitation
  • Scanning transmission electron microscopy (STEM)

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