Strengthening mechanisms in aluminum containing coherent Al3Sc precipitates and incoherent Al2O3 dispersoids

Dispersion-strengthened-cast aluminum (DSC-Al), consisting of a coarse-grained aluminum matrix containing two populations of particles (30 vol.% of 300 nm Al2O3 incoherent dispersoids and 0.2-0.3 vol.% of 6-60 nm coherent Al3Sc precipitates), was studied. At ambient and elevated temperatures, both populations of particles contribute to strengthening. At 300 degrees C, creep threshold stresses are considerably higher than for control materials with a single population of either Al2O3 dispersoids or Al3Sc precipitates. This synergistic effect is modeled by considering dislocations pinned at the departure side of incoherent Al2O3 dispersoids (detachment model) and simultaneously subjected to elastic interactions from neighboring coherent Al3Sc precipitates. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.