Abstract
Yield strength at ambient temperature and creep resistance between 225 and 300°C were investigated in dilute Al(Sc) alloys containing coherent Al3Sc precipitates, which were grown by heat-treatments to radii in the range 1.4-9.6 nm. The dependence of the ambient-temperature yield stress on precipitate size is explained using classical precipitation strengthening theory, which predicts a transition from precipitate shearing to Orowan dislocation looping mechanisms at a precipitate radius of 2.1 nm, in good agreement with experimental data. At 300°C creep threshold stresses are observed and found to be much lower than the yield stresses, indicative of a climb-controlled bypass mechanism. The threshold stress increases with increasing precipitate radius, in qualitative agreement with a climb model taking into account stiffness and lattice mismatches between matrix and precipitates.
Original language | English (US) |
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Pages (from-to) | 4021-4035 |
Number of pages | 15 |
Journal | Acta Materialia |
Volume | 50 |
Issue number | 16 |
DOIs | |
State | Published - Sep 20 2002 |
Keywords
- Aluminum alloys
- Creep
- Mechanical properties
- Precipitation strengthening
- Scandium
- Threshold stress
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys