Effect of microadditions of Mn and Mo on dual L12- and α-precipitation in a dilute Al-Zr-Sc-Er-Si alloy

Anthony De Luca*, Shipeng Shu, David N. Seidman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The effects of small additions of 0.25 at.% Mn and 0.11 at.% Mo to a cast, dilute Al-0.08Zr-0.02Sc-0.01Er-0.10Si (at.%) alloy were investigated by Vickers microhardness, electrical conductivity, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Isochronal aging experiments revealed that the Mn/Mo-modifications allowed the alloy to achieve a 30 MPa higher peak microhardness, which was maintained at higher temperatures (475 °C vs. 400 °C). This is attributed to α-Al(Mn,Mo)Si submicron precipitates forming at 450–475 °C, following precipitation of L12-Al3(Zr,Sc,Er) nanoprecipitates at 350–425 °C. Isothermal aging experiments at 400 °C indicated that the Mn/Mo addition improved the coarsening resistance of the L12-precipitates to yield a coarsening rate about four times slower than that found in Mn/Mo-free alloys. Compared to the base alloy, this results in a 30% reduction in the nanoprecipitate radii after six months of aging. The α-phase consists mainly of coherent plate-like precipitates, with a minority of cuboidal semi-coherent precipitates, displaying well-defined crystallographic orientation relationships with the matrix. Increasing the Mn concentration to 0.40 at.%, led to the formation of primary Al12(Mn,Mo) precipitates, which are too coarse to provide any strength benefit.

Original languageEnglish (US)
Article number110585
JournalMaterials Characterization
StatePublished - Nov 2020


  • Al-Zr-Sc-Er-Si-Mn-Mo alloy
  • High-temperature alloy
  • Precipitation strengthening
  • Transmission electron microscopy

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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