Effect of Si micro-addition on creep resistance of a dilute Al-Sc-Zr-Er alloy

Nhon Q. Vo, David N. Seidman, David C. Dunand*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


A dilute Al-0.06Sc-0.02Zr-0.005Er (at%) alloy, to which 0.09 at% Si was added, was peak-aged to create a high number density of (Al,Si)3(ScEr,Zr) precipitates, 3.6 nm in radius. The alloy shows a high resistance to dislocation creep, with a threshold stress of 18 MPa at 400 °C. After further aging under applied stress for ~ 1000 h at 400 °C, the threshold stress increases to 22 MPa, with the precipitates growing to a radius of 4–8 nm. This represents a very substantial improvement in creep resistance as compared to a similar alloy with one-third the Si content, 0.03 at%, whose threshold stress at 400 °C is 9–14 MPa. Atom probe tomography reveals that, for the new higher-Si alloy, the precipitates have an average Si concentration of 3.3 at% and show a broad core with uniform Sc-, Si- and Er concentrations and a thin Zr-enriched shell. By contrast, the low-Si alloy exhibits precipitates with half the average Si content, showing an Er-enriched core, a Sc-enriched inner-shell and a Zr-enriched outer-shell. A possible explanation for the higher creep resistance of the high-Si alloy is that the enhanced chemical homogeneity of Sc and Er in the core, as compared to the highly segregated core/shell/shell structure of the low-Si alloy, modifies the elastic strain field around precipitates so as to increase the repulsive force from the precipitate on the matrix dislocations climbing over them, thus enhancing the threshold creep stresses.

Original languageEnglish (US)
Pages (from-to)27-33
Number of pages7
JournalMaterials Science and Engineering A
StatePublished - Sep 12 2018


  • Al-Sc-Zr-Er-Si alloy
  • Atom-probe tomography
  • Creep
  • High-temperature alloy
  • Precipitation strengthening

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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