Abstract
Precipitation of the Al3Sc (L12) phase in aluminum alloys, containing 0.1, 0.2 or 0.3 wt% Sc, is studied with conventional transmission and high-resolution (HREM) electron microscopies. The exact morphologies of the Al3Sc precipitates were determined for the first time by HREM, in Al-0.1 wt% Sc and Al-0.3 wt% Sc alloys. The experimentally determined equilibrium shape of the Al3Sc precipitates, at 300°C and 0.3 wt% Sc, has 26 facets, which are the 6 {100} (cube), 12 {110} (rhombic dodecahedron), and 8 {111} (octahedron) planes, a Great Rhombicuboctahedron. This equilibrium morphology had been predicted by first principles calculations of the pertinent interfacial energies. The coarsening kinetics obey the (time)1/3 kinetic law of Lifshitz-Slyozov-Wagner theory and they yield an activation energy for diffusion, 164±9 kJ/mol, that is in agreement with the values obtained from tracer diffusion measurements of Sc in Al and first principles calculations, which implies diffusion-controlled coarsening.
Original language | English (US) |
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Pages (from-to) | 1909-1919 |
Number of pages | 11 |
Journal | Acta Materialia |
Volume | 49 |
Issue number | 11 |
DOIs | |
State | Published - Jun 22 2001 |
Keywords
- Aluminum
- Microstructure
- Phase transformations
- Scandium
- Transmission electron microscopy (TEM)
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys