Improving creep resistance of Al-12 wt.% Ce alloy by microalloying with Sc

The near-eutectic Al-12 wt.% Ce alloy has been alloyed with 0.4 wt.% Sc to improve its creep resistance. A bidirectional influence between Sc and Ce has been identified: (i) the Ce element suppresses the Sc partition between the liquid and solid phases during solidification, as implied by the reduction of Sc microsegregation in the as-cast ingot; (ii) the Sc atoms migrate towards the Al₁₁Ce₃ interface to form Al₃Sc thin layer or particles upon aging. The former effect promotes the spatial uniformity of Al₃Sc precipitate distribution in the Al matrix and the latter one introduces additional lattice misfit strain to the Al₁₁Ce₃/Al_α phase boundary inhibiting matrix dislocations to climb over the Al₁₁Ce₃ lamellae. Both effects can improve the creep resistance of the aged Al-12Ce-0.4Sc alloy showing a high tensile stress threshold for dislocation creep of ∼ 60 MPa at 300 ^∘C.