Size effect in the Al3Sc dispersoid-mediated precipitation and mechanical/electrical properties of Al-Mg-Si-Sc alloys

Abstract A significant size effect is found in the Al3Sc dispersoid-mediated precipitation in an Al-Mg-Si-Sc alloy. When the Al3Sc dispersoid size smaller than about 40 nm, β″ precipitates nucleate directly on the coherent dispersoids and grow by sacrificing the latter. While the dispersoid size greater than ∼ 40 nm, Q' and U2 phases are additionally produced that nucleate on the dislocations induced by the semi-/incoherent dispersoids. Mechanical and electrical properties are highly sensitive to the Al3Sc dispersoid-tuned precipitation. The co-precipitation of β″, Q' and U2 phases lead to an obvious improvement in hardness and simultaneously in electrical conductivity.