On the role of tin in promoting nucleation of the θ′ phase in Al-Cu-Sn

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The role of tin (Sn) in assisting the nucleation of the plate-shaped precipitate phase θ′ in an Al-4Cu-0.05Sn (wt%) alloy has been investigated by high resolution transmission electron microscopy (HRTEM) and three-dimensional atom probe field ion microscopy (3D-APFIM). HRTEM revealed that the strong contrast on the rim of many θ′ precipitates in underaged alloys may be attributed to formation of a Sn particle, possibly the β-Sn phase, with an orientation relationship with respect to the aluminium matrix that is different to that commonly accepted. 3D-APFIM revealed local zones containing an enrichment of Sn atoms, but a majority of aluminium atoms, suggesting that it is small clusters of Sn atoms, and not the β-Sn phase, that are involved in lowering the nucleation barrier for the θ′ phase. This interpretation is supported by the HRTEM observation that, even before nucleation of most of the θ′ phase, very few Sn particles are found independent of θ′ precipitates.

Original languageEnglish
Pages (from-to)789-794
Number of pages6
JournalMaterials Science Forum
Issue number2
Publication statusPublished - 3 Dec 2002
EventAluminium Alloys 2002 Their Physical and Mechnaical Properties: Proceedings of the 8th International Conference ICAA8 - Cambridge, United Kingdom
Duration: 2 Jul 20025 Jul 2002


  • 3D Atom Probe Field Ion Microscopy
  • Aluminium Alloy
  • High-Resolution Transmission Electron Microscopy
  • Microalloying
  • Nucleation

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