Effect of micro-additions of Ge, In or Sn on precipitation in dilute Al-Sc-Zr alloys

Philipp Okle, Jeffrey D. Lin, Tianyu Zhu, David C Dunand, David N Seidman

Research output: Contribution to journalArticle

Abstract

Trace amounts of inoculants - germanium (0.02 at%), indium (0.02 at%) or tin (0.01 at%) - were added to a ternary Al-0.06Sc-0.06Zr at% alloy to study their effects on Al3(Sc,Zr) precipitation. During isothermal aging at 300 °C, the In- and Sn-containing alloys exhibit an early microhardness increases, which is attributed to In or Sn clustering. Peak isothermal microhardness due to Al3(Sc,Zr) precipitation is achieved simultaneously (~4 h) for the three inoculated alloys and an inoculant-free alloy. Isochronal aging produces a low-temperature microhardening response for the In- and Sn-containing alloys, followed by two microhardness peaks at 350 and 450 °C for all four alloys, associated with precipitation of Sc and Zr, respectively. Atom-probe tomography demonstrates partitioning of Ge and Sn (up to 0.5 at%) from the matrix to the Al3(Sc,Zr) precipitates, with partitioning to Sc-rich precipitate cores (for isothermal aging) or to both Sc-rich cores and Zr-rich shells (for isochronal aging). Inoculant partitioning at precipitate cores and early low-temperature microhardness increases are consistent with inoculant clustering to form nucleation sites for Sc and Zr precipitation. Inoculant segregation at the precipitate shells can be explained by co-precipitation of the fast-diffusing inoculant element and the slow-diffusing Zr, between which an attractive binding energy exists. When compared to the inoculant-free control alloy with a somewhat higher Sc content, the three inoculated alloys exhibit a 2- to 10-fold decrease in creep rates at 300 °C for stresses above ~18 MPa, but a small reduction in creep threshold stresses from 12 to ~10 MPa.

LanguageEnglish (US)
Pages427-436
Number of pages10
JournalMaterials Science and Engineering A
Volume739
DOIs
StatePublished - Jan 2 2019

Fingerprint

Microhardness
microhardness
Precipitates
precipitates
Aging of materials
Creep
Germanium
Indium
Tin
Coprecipitation
Binding energy
Tomography
indium
germanium
tin
Nucleation
tomography
binding energy
nucleation
Atoms

Keywords

  • Aluminum alloys
  • Atom probe
  • Microhardness
  • Scandium
  • Zirconium

ASJC Scopus subject areas

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

Cite this

@article{341505cf3398474fa5c019c961d6796b,
title = "Effect of micro-additions of Ge, In or Sn on precipitation in dilute Al-Sc-Zr alloys",
abstract = "Trace amounts of inoculants - germanium (0.02 at{\%}), indium (0.02 at{\%}) or tin (0.01 at{\%}) - were added to a ternary Al-0.06Sc-0.06Zr at{\%} alloy to study their effects on Al3(Sc,Zr) precipitation. During isothermal aging at 300 °C, the In- and Sn-containing alloys exhibit an early microhardness increases, which is attributed to In or Sn clustering. Peak isothermal microhardness due to Al3(Sc,Zr) precipitation is achieved simultaneously (~4 h) for the three inoculated alloys and an inoculant-free alloy. Isochronal aging produces a low-temperature microhardening response for the In- and Sn-containing alloys, followed by two microhardness peaks at 350 and 450 °C for all four alloys, associated with precipitation of Sc and Zr, respectively. Atom-probe tomography demonstrates partitioning of Ge and Sn (up to 0.5 at{\%}) from the matrix to the Al3(Sc,Zr) precipitates, with partitioning to Sc-rich precipitate cores (for isothermal aging) or to both Sc-rich cores and Zr-rich shells (for isochronal aging). Inoculant partitioning at precipitate cores and early low-temperature microhardness increases are consistent with inoculant clustering to form nucleation sites for Sc and Zr precipitation. Inoculant segregation at the precipitate shells can be explained by co-precipitation of the fast-diffusing inoculant element and the slow-diffusing Zr, between which an attractive binding energy exists. When compared to the inoculant-free control alloy with a somewhat higher Sc content, the three inoculated alloys exhibit a 2- to 10-fold decrease in creep rates at 300 °C for stresses above ~18 MPa, but a small reduction in creep threshold stresses from 12 to ~10 MPa.",
keywords = "Aluminum alloys, Atom probe, Microhardness, Scandium, Zirconium",
author = "Philipp Okle and Lin, {Jeffrey D.} and Tianyu Zhu and Dunand, {David C} and Seidman, {David N}",
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Effect of micro-additions of Ge, In or Sn on precipitation in dilute Al-Sc-Zr alloys. / Okle, Philipp; Lin, Jeffrey D.; Zhu, Tianyu; Dunand, David C; Seidman, David N.

In: Materials Science and Engineering A, Vol. 739, 02.01.2019, p. 427-436.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effect of micro-additions of Ge, In or Sn on precipitation in dilute Al-Sc-Zr alloys

AU - Okle, Philipp

AU - Lin, Jeffrey D.

AU - Zhu, Tianyu

AU - Dunand, David C

AU - Seidman, David N

PY - 2019/1/2

Y1 - 2019/1/2

N2 - Trace amounts of inoculants - germanium (0.02 at%), indium (0.02 at%) or tin (0.01 at%) - were added to a ternary Al-0.06Sc-0.06Zr at% alloy to study their effects on Al3(Sc,Zr) precipitation. During isothermal aging at 300 °C, the In- and Sn-containing alloys exhibit an early microhardness increases, which is attributed to In or Sn clustering. Peak isothermal microhardness due to Al3(Sc,Zr) precipitation is achieved simultaneously (~4 h) for the three inoculated alloys and an inoculant-free alloy. Isochronal aging produces a low-temperature microhardening response for the In- and Sn-containing alloys, followed by two microhardness peaks at 350 and 450 °C for all four alloys, associated with precipitation of Sc and Zr, respectively. Atom-probe tomography demonstrates partitioning of Ge and Sn (up to 0.5 at%) from the matrix to the Al3(Sc,Zr) precipitates, with partitioning to Sc-rich precipitate cores (for isothermal aging) or to both Sc-rich cores and Zr-rich shells (for isochronal aging). Inoculant partitioning at precipitate cores and early low-temperature microhardness increases are consistent with inoculant clustering to form nucleation sites for Sc and Zr precipitation. Inoculant segregation at the precipitate shells can be explained by co-precipitation of the fast-diffusing inoculant element and the slow-diffusing Zr, between which an attractive binding energy exists. When compared to the inoculant-free control alloy with a somewhat higher Sc content, the three inoculated alloys exhibit a 2- to 10-fold decrease in creep rates at 300 °C for stresses above ~18 MPa, but a small reduction in creep threshold stresses from 12 to ~10 MPa.

AB - Trace amounts of inoculants - germanium (0.02 at%), indium (0.02 at%) or tin (0.01 at%) - were added to a ternary Al-0.06Sc-0.06Zr at% alloy to study their effects on Al3(Sc,Zr) precipitation. During isothermal aging at 300 °C, the In- and Sn-containing alloys exhibit an early microhardness increases, which is attributed to In or Sn clustering. Peak isothermal microhardness due to Al3(Sc,Zr) precipitation is achieved simultaneously (~4 h) for the three inoculated alloys and an inoculant-free alloy. Isochronal aging produces a low-temperature microhardening response for the In- and Sn-containing alloys, followed by two microhardness peaks at 350 and 450 °C for all four alloys, associated with precipitation of Sc and Zr, respectively. Atom-probe tomography demonstrates partitioning of Ge and Sn (up to 0.5 at%) from the matrix to the Al3(Sc,Zr) precipitates, with partitioning to Sc-rich precipitate cores (for isothermal aging) or to both Sc-rich cores and Zr-rich shells (for isochronal aging). Inoculant partitioning at precipitate cores and early low-temperature microhardness increases are consistent with inoculant clustering to form nucleation sites for Sc and Zr precipitation. Inoculant segregation at the precipitate shells can be explained by co-precipitation of the fast-diffusing inoculant element and the slow-diffusing Zr, between which an attractive binding energy exists. When compared to the inoculant-free control alloy with a somewhat higher Sc content, the three inoculated alloys exhibit a 2- to 10-fold decrease in creep rates at 300 °C for stresses above ~18 MPa, but a small reduction in creep threshold stresses from 12 to ~10 MPa.

KW - Aluminum alloys

KW - Atom probe

KW - Microhardness

KW - Scandium

KW - Zirconium

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JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

SN - 0921-5093

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