Microstructure and mechanical properties of a precipitation-strengthened Al-Zr-Sc-Er-Si alloy with a very small Sc content

Anthony De Luca*, David C Dunand, David N Seidman

*Corresponding author for this work

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The precipitation hardening behavior of an Al-0.08Zr-0.014Sc-0.008Er-0.10Si (at.%) alloy was investigated utilizing microhardness, electrical conductivity, atom-probe tomography (APT), and compressive creep-measurements. This new composition, with a Sc:Zr atomic ratio of less than 1:5 represents a significant reduction of the alloy's cost when compared to the more usual Al-0.06Sc-0.02Zr based alloys with typical Sc:Zr atomic ratios of 3:1. To study the precipitation behavior of this low-Sc alloy, isothermal aging experiments between 350 and 425 °C for a duration of up to 6 months were performed. The low concentration of Sc, compensated by the high Zr concentration, permits the alloy to achieve a higher peak microhardness than the corresponding Sc-richer, Zr-leaner alloys. The low-Sc alloy also shows better over aging resistance, as anticipated from the smaller diffusivity of Zr when compared to Sc, leading to slower coarsening kinetics. Atom-probe tomography demonstrates that the high microhardness is due to the formation of a high number density of nano-precipitates, ∼1023 m−3 for peak aging conditions, with a mean radius of 1.9 nm, thus yielding a high volume fraction (0.35%) of nano-precipitates. Like alloys with much higher Sc and Er concentrations, the (Al,Si)3(Sc,Zr,Er) nano-precipitates still exhibit a core-shell structure with a concentration of Zr in the shell of up to 25 at.%, and a Sc- and Er-enriched core. Compressive creep experiments at 300 °C demonstrate that the new alloy, with only 0.014 at% Sc, is as creep resistant as a binary Al-0.08Sc at.% alloy, displaying a threshold stress of 17.5 ± 0.6 MPa at peak aged condition.

Original languageEnglish (US)
Pages (from-to)80-91
Number of pages12
JournalActa Materialia
Volume144
DOIs
StatePublished - Feb 1 2018

Fingerprint

Mechanical properties
Microstructure
Microhardness
Precipitates
Creep
Aging of materials
Tomography
Atoms
Age hardening
Coarsening
Volume fraction
Experiments
Kinetics
Chemical analysis
Costs

Keywords

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

ASJC Scopus subject areas

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

Cite this

@article{00b94be5a87b467e83234492704572c3,
title = "Microstructure and mechanical properties of a precipitation-strengthened Al-Zr-Sc-Er-Si alloy with a very small Sc content",
abstract = "The precipitation hardening behavior of an Al-0.08Zr-0.014Sc-0.008Er-0.10Si (at.{\%}) alloy was investigated utilizing microhardness, electrical conductivity, atom-probe tomography (APT), and compressive creep-measurements. This new composition, with a Sc:Zr atomic ratio of less than 1:5 represents a significant reduction of the alloy's cost when compared to the more usual Al-0.06Sc-0.02Zr based alloys with typical Sc:Zr atomic ratios of 3:1. To study the precipitation behavior of this low-Sc alloy, isothermal aging experiments between 350 and 425 °C for a duration of up to 6 months were performed. The low concentration of Sc, compensated by the high Zr concentration, permits the alloy to achieve a higher peak microhardness than the corresponding Sc-richer, Zr-leaner alloys. The low-Sc alloy also shows better over aging resistance, as anticipated from the smaller diffusivity of Zr when compared to Sc, leading to slower coarsening kinetics. Atom-probe tomography demonstrates that the high microhardness is due to the formation of a high number density of nano-precipitates, ∼1023 m−3 for peak aging conditions, with a mean radius of 1.9 nm, thus yielding a high volume fraction (0.35{\%}) of nano-precipitates. Like alloys with much higher Sc and Er concentrations, the (Al,Si)3(Sc,Zr,Er) nano-precipitates still exhibit a core-shell structure with a concentration of Zr in the shell of up to 25 at.{\%}, and a Sc- and Er-enriched core. Compressive creep experiments at 300 °C demonstrate that the new alloy, with only 0.014 at{\%} Sc, is as creep resistant as a binary Al-0.08Sc at.{\%} alloy, displaying a threshold stress of 17.5 ± 0.6 MPa at peak aged condition.",
keywords = "Al-Zr-Sc-Er-Si alloy, Atom-probe tomography, High-temperature alloy, Mechanical properties, Precipitation strengthening",
author = "{De Luca}, Anthony and Dunand, {David C} and Seidman, {David N}",
year = "2018",
month = "2",
day = "1",
doi = "10.1016/j.actamat.2017.10.040",
language = "English (US)",
volume = "144",
pages = "80--91",
journal = "Acta Materialia",
issn = "1359-6454",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Microstructure and mechanical properties of a precipitation-strengthened Al-Zr-Sc-Er-Si alloy with a very small Sc content

AU - De Luca, Anthony

AU - Dunand, David C

AU - Seidman, David N

PY - 2018/2/1

Y1 - 2018/2/1

N2 - The precipitation hardening behavior of an Al-0.08Zr-0.014Sc-0.008Er-0.10Si (at.%) alloy was investigated utilizing microhardness, electrical conductivity, atom-probe tomography (APT), and compressive creep-measurements. This new composition, with a Sc:Zr atomic ratio of less than 1:5 represents a significant reduction of the alloy's cost when compared to the more usual Al-0.06Sc-0.02Zr based alloys with typical Sc:Zr atomic ratios of 3:1. To study the precipitation behavior of this low-Sc alloy, isothermal aging experiments between 350 and 425 °C for a duration of up to 6 months were performed. The low concentration of Sc, compensated by the high Zr concentration, permits the alloy to achieve a higher peak microhardness than the corresponding Sc-richer, Zr-leaner alloys. The low-Sc alloy also shows better over aging resistance, as anticipated from the smaller diffusivity of Zr when compared to Sc, leading to slower coarsening kinetics. Atom-probe tomography demonstrates that the high microhardness is due to the formation of a high number density of nano-precipitates, ∼1023 m−3 for peak aging conditions, with a mean radius of 1.9 nm, thus yielding a high volume fraction (0.35%) of nano-precipitates. Like alloys with much higher Sc and Er concentrations, the (Al,Si)3(Sc,Zr,Er) nano-precipitates still exhibit a core-shell structure with a concentration of Zr in the shell of up to 25 at.%, and a Sc- and Er-enriched core. Compressive creep experiments at 300 °C demonstrate that the new alloy, with only 0.014 at% Sc, is as creep resistant as a binary Al-0.08Sc at.% alloy, displaying a threshold stress of 17.5 ± 0.6 MPa at peak aged condition.

AB - The precipitation hardening behavior of an Al-0.08Zr-0.014Sc-0.008Er-0.10Si (at.%) alloy was investigated utilizing microhardness, electrical conductivity, atom-probe tomography (APT), and compressive creep-measurements. This new composition, with a Sc:Zr atomic ratio of less than 1:5 represents a significant reduction of the alloy's cost when compared to the more usual Al-0.06Sc-0.02Zr based alloys with typical Sc:Zr atomic ratios of 3:1. To study the precipitation behavior of this low-Sc alloy, isothermal aging experiments between 350 and 425 °C for a duration of up to 6 months were performed. The low concentration of Sc, compensated by the high Zr concentration, permits the alloy to achieve a higher peak microhardness than the corresponding Sc-richer, Zr-leaner alloys. The low-Sc alloy also shows better over aging resistance, as anticipated from the smaller diffusivity of Zr when compared to Sc, leading to slower coarsening kinetics. Atom-probe tomography demonstrates that the high microhardness is due to the formation of a high number density of nano-precipitates, ∼1023 m−3 for peak aging conditions, with a mean radius of 1.9 nm, thus yielding a high volume fraction (0.35%) of nano-precipitates. Like alloys with much higher Sc and Er concentrations, the (Al,Si)3(Sc,Zr,Er) nano-precipitates still exhibit a core-shell structure with a concentration of Zr in the shell of up to 25 at.%, and a Sc- and Er-enriched core. Compressive creep experiments at 300 °C demonstrate that the new alloy, with only 0.014 at% Sc, is as creep resistant as a binary Al-0.08Sc at.% alloy, displaying a threshold stress of 17.5 ± 0.6 MPa at peak aged condition.

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

KW - Atom-probe tomography

KW - High-temperature alloy

KW - Mechanical properties

KW - Precipitation strengthening

UR - http://www.scopus.com/inward/record.url?scp=85032815974&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85032815974&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2017.10.040

DO - 10.1016/j.actamat.2017.10.040

M3 - Article

VL - 144

SP - 80

EP - 91

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -