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 journalArticle

3 Citations (Scopus)

Abstract

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
Volume734
DOIs
StatePublished - Sep 12 2018

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creep strength
Creep resistance
Precipitates
precipitates
thresholds
Creep
radii
high resistance
homogeneity
Tomography
tomography
Aging of materials
Atoms
probes
matrices
atoms

Keywords

  • 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

Cite this

@article{5c530f47d86c4e449acc1ad5050499b7,
title = "Effect of Si micro-addition on creep resistance of a dilute Al-Sc-Zr-Er alloy",
abstract = "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.",
keywords = "Al-Sc-Zr-Er-Si alloy, Atom-probe tomography, Creep, High-temperature alloy, Precipitation strengthening",
author = "Vo, {Nhon Q.} and Seidman, {David N} and Dunand, {David C}",
year = "2018",
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day = "12",
doi = "10.1016/j.msea.2018.07.053",
language = "English (US)",
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Effect of Si micro-addition on creep resistance of a dilute Al-Sc-Zr-Er alloy. / Vo, Nhon Q.; Seidman, David N; Dunand, David C.

In: Materials Science and Engineering A, Vol. 734, 12.09.2018, p. 27-33.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effect of Si micro-addition on creep resistance of a dilute Al-Sc-Zr-Er alloy

AU - Vo, Nhon Q.

AU - Seidman, David N

AU - Dunand, David C

PY - 2018/9/12

Y1 - 2018/9/12

N2 - 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.

AB - 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.

KW - Al-Sc-Zr-Er-Si alloy

KW - Atom-probe tomography

KW - Creep

KW - High-temperature alloy

KW - Precipitation strengthening

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U2 - 10.1016/j.msea.2018.07.053

DO - 10.1016/j.msea.2018.07.053

M3 - Article

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SP - 27

EP - 33

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

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

SN - 0921-5093

ER -