Precipitation reactions in Al-4.0Cu-0.3Mg (wt.%) alloy

S. P. Ringer, B. T. Sofyan, K. S. Prasad, G. C. Quan

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60 Citations (Scopus)

Abstract

Analytical transmission electron microscopy was used to characterize precipitation processes in a model Al-4.0Cu-0.3Mg (wt.%) alloy aged at 200 °C. The evolution of microstructure was more complex than previously reported and involved processes common both to the binary Al-Cu and ternary Al-Cu-Mg systems. We report precipitation of a novel orientation of the common intermediate phase θ′, which we have designated θII. Isomorphous with the well-known body-centred tetragonal Al2Cu phase that occurs in Al-Cu-based alloys, we observed the following novel orientation: {0 0 1}θII′ / / {1 1 0}α, 〈 1 0 0 〉θII′ / / 〈 0 0 1 〉α. A trace of Mg was associated with the θII orientation and we suggest that this is a consequence of the role that Mg atom clusters play during nucleation. For the first time, we also report the occurrence of the σ phase (Al5Cu6Mg2) in a new orientation analogous to that of θII, designated as σII: {0 0 1}α / / {0 0 1}σII and 〈 1 1 0 〉α / / 〈 0 1 0 〉σII. These results are discussed in terms of microstructural design for age hardening in Al-Cu-Mg base alloys, much of which involves the θ′ and σ precipitate phases.

Original languageEnglish
Pages (from-to)2147-2160
Number of pages14
JournalActa Materialia
Volume56
Issue number9
DOIs
Publication statusPublished - 1 May 2008

Keywords

  • Age hardening
  • Cluster assisted nucleation
  • Microstructure
  • Precipitation
  • TEM

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