The Effect of Scandium on the Microstructure of the Aluminium Alloy AA 6086

Sandi Zist, Matej Steinacher, Tonica Bončina, Mihaela Albu, Jaka Burja, Maja Voncina, Franc Zupanič

Research output: Contribution to journalArticlepeer-review


The investigation studied the effects of 0.2 wt.% and 1 wt.% scandium (Sc) additions on the microstructure of the aluminium alloy AA 6086 in different conditions. The alloys were produced by casting into a metallic mould, followed by various heat treatments. The alloys were examined using light microscopy, scanning and transmission electron microscopy, microchemical analysis, differential scanning calorimetry and X-ray diffraction. The phase compositions and solidification sequences were modelled using the CALPHAD approach, which reasonably agreed with the experimental results. The addition of Sc to AA 6086 strongly reduced the grain size of the Al-rich solid solution and induced the appearance of Sc-rich phases AlSc 2Si 2 and L1 2-Al 3X. Other phases identified in the Sc-free alloy were also found in the Sc-modified alloys. Homogenisation caused the dissolution of most phases and the formation of different types of dispersoids. In the alloy with 0.2% Sc, the distribution of dispersoids was not uniform. The plate-like AlMnCrSi dispersoids formed mainly at the dendrite centres, together with spherical L1 2 precipitates, while smaller α-AlMnSi and tetragonal t-Al 3Zr dispersoids were created elsewhere. The addition of 0.2% Sc did not considerably affect the strengthening of AA 6086. The precipitation during isothermal ageing was slightly delayed and shifted to higher temperatures during continuous heating.

Original languageEnglish
Article number973
Number of pages21
Issue number7
Publication statusPublished - Jul 2022


  • ageing
  • alloying
  • aluminium
  • dispersoid
  • microscopy
  • microstructure
  • solidification

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Chemical Engineering(all)
  • Inorganic Chemistry

Fields of Expertise

  • Advanced Materials Science

Treatment code (Nähere Zuordnung)

  • Basic - Fundamental (Grundlagenforschung)

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