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van Dalen, Marsha E.; Dunand, David C.; Seidman, David N. |
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Publication |
Nanoscale Precipitation and Mechanical Properties of Al-0.06 at.% Sc Alloys Micro-Alloyed with Yb or Gd |
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Journal Article |
Pages |
2006 |
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Abstract |
Journal of Materials Science |
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41 |
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23 |
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Summary Language |
7814-7823 |
Series Editor |
Aluminum alloys; Precipitation; Nucleation; Three-dimensional atom-probe tomography; Rare earth elements; Al-Sc |
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Abbreviated Series Title |
Dilute Al-0.06 at.% Sc alloys with micro-alloying additions of 50 at. ppm of Yb or Gd
are studied with 3-D local-electrode atom-probe (LEAP) tomography for different aging
times at 300C. Peak-aged alloys exhibit Al3(Sc1-xYbx) or Al3(Sc1-xGdx) precipitates (L12
structure) with a much higher number density (and therefore higher peak hardness) than a
binary Al-0.06 at.% Sc alloy. The Al-Sc-Gd alloy exhibits a higher number density of
precipitates with a smaller average radius than the Al-Sc-Yb alloy, leading to a higher
hardness. In the Al-Sc-Gd alloy, only a small amount of the Sc is replaced by Gd in the
Al3(Sc1-xGdx) precipitates, where x = 8.0%. By contrast, the hardness incubation time is
significantly shorter in the Al-Sc-Yb alloy, due to the formation of Yb-rich Al3(Yb1-xScx)
precipitates to which Sc subsequently diffuses, eventually forming Sc-rich Al3(Sc1-xYbx)
precipitates. For both alloys, precipitate radii are found to be relatively stable up to 24 h
of aging, although the concentration and distribution of the RE elements in the
precipitates continues to evolve temporally. Similar to microhardness at ambient
temperature, the creep resistance at 300C is significantly improved by RE microalloying
of the binary Al-Sc alloy. |
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767 |
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