Precipitation strengthening at ambient and elevated temperatures of heat-treatable Al(Sc) alloys

• Published in: Acta materialia 2002-09, Vol.50 (16), p.4021-4035
• Main Authors: Seidman, David N., Marquis, Emmanuelle A., Dunand, David C.
• Format: Article
• Language: English
• Subjects: Aluminum alloys; Applied sciences; Creep; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Mechanical properties; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Precipitation strengthening; Scandium; Solid-phase precipitation; Threshold stress
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(02)00201-X

Yield strength at ambient temperature and creep resistance between 225 and 300°C were investigated in dilute Al(Sc) alloys containing coherent Al 3Sc 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 [1].