BSTRACTCommercial precipitation-hardened Al-Cu alloys are normally used at temperatures below its ageing temperature of ∼225°C

to avoid thermally induced precipitate coarsening and resultant softening. Making such popular Al alloys creep resistant at or above 300°C is thus challenging. Here we present a modified precipitation protocol

exploiting Sc-microalloying and a carefully designed three-step heat treatment to enhance Sc segregation at the matrix/

θ′-

Al

2

Cu precipitate interfaces. The stabilized nanoprecipitates enable an order-of-magnitude reduction in creep rate at 300°C

demonstrating the room for microstructure improvement and the potential for property elevation in traditional engineering alloys through innovative processing coupled with synergetic alloying elements.