Role of silicon in accelerating the nucleation of Al 3(Sc,Zr) precipitates in dilute Al-Sc-Zr alloys

C. Booth-Morrison, Z. Mao, M. Diaz, David C Dunand, Christopher M Wolverton, David N Seidman*

*Corresponding author for this work

Research output: Contribution to journalArticle

90 Scopus citations

Abstract

The effects of adding 0.02 or 0.06 at.% Si to Al-0.06Sc-0.06Zr (at.%) are studied to determine the impact of Si on accelerating Al 3(Sc,Zr) precipitation kinetics in dilute Al-Sc-based alloys. Precipitation in the 0.06 at.% Si alloy, measured by microhardness and atom-probe tomography (APT), is accelerated for aging times <4 h at 275 and 300 °C, compared with the 0.02 at.% Si alloy. Experimental partial radial distribution functions of the α-Al matrix of the high-Si alloy reveal considerable Si-Sc clustering, which is attributed to attractive Si-Sc binding energies at the first and second nearest-neighbor distances, as confirmed by first-principles calculations. Calculations also indicate that Si-Sc binding decreases both the vacancy formation energy near Sc and the Sc migration energy in Al. APT further demonstrates that Si partitions preferentially to the Sc-enriched core rather than the Zr-enriched shell in the core/shell Al 3(Sc,Zr) (L1 2) precipitates in the high-Si alloy subjected to double aging (8 h/300 °C for Sc precipitation and 32 days/400 °C for Zr precipitation). Calculations of the driving force for Si partitioning confirm that: (i) Si partitions preferentially to the Al 3(Sc,Zr) (L1 2) precipitates, occupying the Al sublattice site; (ii) Si increases the driving force for the precipitation of Al 3Sc; and (iii) Si partitions preferentially to Al 3Sc (L1 2) rather than Al 3Zr (L1 2).

Original languageEnglish (US)
Pages (from-to)4740-4752
Number of pages13
JournalActa Materialia
Volume60
Issue number12
DOIs
StatePublished - Jul 1 2012

Keywords

  • Aluminum alloys
  • Precipitation kinetics
  • Scandium
  • Silicon
  • Zirconium

ASJC Scopus subject areas

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

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