Effect of Mg addition on the creep and yield behavior of an Al-Sc alloy

Emmanuelle A. Marquis*, David N. Seidman, David C. Dunand

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

123 Scopus citations


The relationships between microstructure and strength were studied at room temperature and 300 °C in an Al-2 wt% Mg-0.2 wt% Sc alloy, containing Mg in solid-solution and Al3Sc (L12 structure) as nanosize precipitates. At room temperature, the yield strength is controlled by the superposition of solid-solution and precipitation strengthening. At 300 °C and at large applied stresses, the creep strength, which is characterized by a stress exponent of ∼ 5, is significantly improved compared to binary Al-Sc alloys, and is independent of the size of the Al3Sc precipitates. At small applied stress, a threshold stress exists, increasing from 9% to 70% of the Orowan stress with increasing Al3Sc precipitate radius from 2 to 25 nm. An existing model based on a climb-controlled bypass mechanism is in semi-quantitative agreement with the precipitate radius dependence of the threshold stress. The model is, however, only valid for coherent precipitates, and the Al3Sc precipitates lose coherency for radii larger than 11 nm. For semi-coherent precipitates with radii greater than 15 nm, the threshold stress remains high, most likely because of the presence of interfacial misfit dislocations.

Original languageEnglish (US)
Pages (from-to)4751-4760
Number of pages10
JournalActa Materialia
Issue number16
StatePublished - Sep 15 2003


  • Al Sc precipitates
  • Aluminum alloys
  • Coarsening
  • Creep
  • Transmission electron microscopy

ASJC Scopus subject areas

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

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