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 language | English (US) |
|---|---|
| Pages (from-to) | 1-14 |
| Number of pages | 14 |
| Journal | Acta Materialia |
| Volume | 165 |
| DOIs | |
| State | Published - Feb 15 2019 |
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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
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Effects of Mo and Mn microadditions on strengthening and over-aging resistance of nanoprecipitation-strengthened Al-Zr-Sc-Er-Si alloys. / De Luca, Anthony; Seidman, David N; Dunand, David C.
In: Acta Materialia, Vol. 165, 15.02.2019, p. 1-14.Research output: Contribution to journal › Article
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
M3 - Article
VL - 165
SP - 1
EP - 14
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -