Effects of Mo and Mn microadditions on strengthening and over-aging resistance of nanoprecipitation-strengthened Al-Zr-Sc-Er-Si alloys

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

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Combined microadditions of 0.09 at.% Mo and 0.4 at.% Mn to a dilute Al-0.10Zr-0.01Sc-0.007Er-0.10Si (at.%) alloy lead to increases in strength upon peak-aging, and improved over-aging resistance at 400, 425 and 450 °C for at least 6 months. These improvements are related to four cumulative effects. Firstly, Mn and Mo provide, in the as-cast state, a solid-solution-strengthening contribution of ∼90 MPa. The solid-solution contribution from Mo (∼80 MPa) remains essentially unchanged during aging at 400–450 °C, due to its extremely small diffusivity and precipitation. Secondly, Mn and Mo partition to the cores and shells, respectively, of the nano-size coherent, L12 (Al,Si)3(Zr,Sc,Er) nanoprecipitates, which nucleate in <1 h at 400–450 °C. This is associated with an increase in their number density and a reduction in their growth and coarsening kinetics, thus delaying the loss of strength upon over-aging. Third, Mn and Mo provide precipitation strengthening via submicron α-Al(Mn,Mo)Si precipitates (which form between 1 and 11 days at 400 °C), which counterbalances the loss of Mn solid-solution strengthening. Finally, the α-Al(Mn,Mo)Si precipitates scavenge Si from the matrix, which is then not available to accelerate the coarsening of the L12 precipitates, thereby improving the over-aging resistance of the alloy. Iron additions (0.015 at.%), expected to replace some Mn in the α-phase Al(Fe,Mn,Mo)Si, does not affect the aging behavior.

Original languageEnglish (US)
Pages (from-to)1-14
Number of pages14
JournalActa Materialia
Volume165
DOIs
StatePublished - Feb 15 2019

Fingerprint

Aging of materials
Precipitates
Solid solutions
Coarsening
Lead alloys
Iron
Kinetics

Keywords

  • Al-Zr-Sc-Er-Si-Mn-Mo alloy
  • Atom-probe tomography
  • High-temperature alloy
  • Microhardness
  • Precipitation strengthening

ASJC Scopus subject areas

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

Cite this

@article{52cd0a54b6b342618cb873f89717aa54,
title = "Effects of Mo and Mn microadditions on strengthening and over-aging resistance of nanoprecipitation-strengthened Al-Zr-Sc-Er-Si alloys",
abstract = "Combined microadditions of 0.09 at.{\%} Mo and 0.4 at.{\%} Mn to a dilute Al-0.10Zr-0.01Sc-0.007Er-0.10Si (at.{\%}) alloy lead to increases in strength upon peak-aging, and improved over-aging resistance at 400, 425 and 450 °C for at least 6 months. These improvements are related to four cumulative effects. Firstly, Mn and Mo provide, in the as-cast state, a solid-solution-strengthening contribution of ∼90 MPa. The solid-solution contribution from Mo (∼80 MPa) remains essentially unchanged during aging at 400–450 °C, due to its extremely small diffusivity and precipitation. Secondly, Mn and Mo partition to the cores and shells, respectively, of the nano-size coherent, L12 (Al,Si)3(Zr,Sc,Er) nanoprecipitates, which nucleate in <1 h at 400–450 °C. This is associated with an increase in their number density and a reduction in their growth and coarsening kinetics, thus delaying the loss of strength upon over-aging. Third, Mn and Mo provide precipitation strengthening via submicron α-Al(Mn,Mo)Si precipitates (which form between 1 and 11 days at 400 °C), which counterbalances the loss of Mn solid-solution strengthening. Finally, the α-Al(Mn,Mo)Si precipitates scavenge Si from the matrix, which is then not available to accelerate the coarsening of the L12 precipitates, thereby improving the over-aging resistance of the alloy. Iron additions (0.015 at.{\%}), expected to replace some Mn in the α-phase Al(Fe,Mn,Mo)Si, does not affect the aging behavior.",
keywords = "Al-Zr-Sc-Er-Si-Mn-Mo alloy, Atom-probe tomography, High-temperature alloy, Microhardness, Precipitation strengthening",
author = "{De Luca}, Anthony and Seidman, {David N} and Dunand, {David C}",
year = "2019",
month = "2",
day = "15",
doi = "10.1016/j.actamat.2018.11.031",
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volume = "165",
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TY - JOUR

T1 - Effects of Mo and Mn microadditions on strengthening and over-aging resistance of nanoprecipitation-strengthened Al-Zr-Sc-Er-Si alloys

AU - De Luca, Anthony

AU - Seidman, David N

AU - Dunand, David C

PY - 2019/2/15

Y1 - 2019/2/15

N2 - Combined microadditions of 0.09 at.% Mo and 0.4 at.% Mn to a dilute Al-0.10Zr-0.01Sc-0.007Er-0.10Si (at.%) alloy lead to increases in strength upon peak-aging, and improved over-aging resistance at 400, 425 and 450 °C for at least 6 months. These improvements are related to four cumulative effects. Firstly, Mn and Mo provide, in the as-cast state, a solid-solution-strengthening contribution of ∼90 MPa. The solid-solution contribution from Mo (∼80 MPa) remains essentially unchanged during aging at 400–450 °C, due to its extremely small diffusivity and precipitation. Secondly, Mn and Mo partition to the cores and shells, respectively, of the nano-size coherent, L12 (Al,Si)3(Zr,Sc,Er) nanoprecipitates, which nucleate in <1 h at 400–450 °C. This is associated with an increase in their number density and a reduction in their growth and coarsening kinetics, thus delaying the loss of strength upon over-aging. Third, Mn and Mo provide precipitation strengthening via submicron α-Al(Mn,Mo)Si precipitates (which form between 1 and 11 days at 400 °C), which counterbalances the loss of Mn solid-solution strengthening. Finally, the α-Al(Mn,Mo)Si precipitates scavenge Si from the matrix, which is then not available to accelerate the coarsening of the L12 precipitates, thereby improving the over-aging resistance of the alloy. Iron additions (0.015 at.%), expected to replace some Mn in the α-phase Al(Fe,Mn,Mo)Si, does not affect the aging behavior.

AB - Combined microadditions of 0.09 at.% Mo and 0.4 at.% Mn to a dilute Al-0.10Zr-0.01Sc-0.007Er-0.10Si (at.%) alloy lead to increases in strength upon peak-aging, and improved over-aging resistance at 400, 425 and 450 °C for at least 6 months. These improvements are related to four cumulative effects. Firstly, Mn and Mo provide, in the as-cast state, a solid-solution-strengthening contribution of ∼90 MPa. The solid-solution contribution from Mo (∼80 MPa) remains essentially unchanged during aging at 400–450 °C, due to its extremely small diffusivity and precipitation. Secondly, Mn and Mo partition to the cores and shells, respectively, of the nano-size coherent, L12 (Al,Si)3(Zr,Sc,Er) nanoprecipitates, which nucleate in <1 h at 400–450 °C. This is associated with an increase in their number density and a reduction in their growth and coarsening kinetics, thus delaying the loss of strength upon over-aging. Third, Mn and Mo provide precipitation strengthening via submicron α-Al(Mn,Mo)Si precipitates (which form between 1 and 11 days at 400 °C), which counterbalances the loss of Mn solid-solution strengthening. Finally, the α-Al(Mn,Mo)Si precipitates scavenge Si from the matrix, which is then not available to accelerate the coarsening of the L12 precipitates, thereby improving the over-aging resistance of the alloy. Iron additions (0.015 at.%), expected to replace some Mn in the α-phase Al(Fe,Mn,Mo)Si, does not affect the aging behavior.

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

KW - Atom-probe tomography

KW - High-temperature alloy

KW - Microhardness

KW - Precipitation strengthening

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U2 - 10.1016/j.actamat.2018.11.031

DO - 10.1016/j.actamat.2018.11.031

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JF - Acta Materialia

SN - 1359-6454

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