Effect of Yb microadditions on creep resistance of a dilute Al-Er-Sc-Zr alloy

A dilute Al-0.02Yb-0.01Er-0.03Sc-0.03Zr (at.%) alloy was aged to create a high number density of Al-3 (Sc0.56Yb0.14Er0.10Zr0.20) nanoprecipitates, with 3.5 nm radius, an Yb- and Er-enriched core and Sc- and Zr- enriched shells, as measured via atom-probe tomography. At 400 degrees C, the alloy exhibits a 17 MPa threshold stress, 2-3 times higher than previously-studied, Sc-richer Al-0.06Sc-0.06Zr and Al-0.01Er-0.05Sc-0.06Zr (at.%) alloys with Al-3 (Sc,Zr) and Al-3 (Sc,Zr,Er) nanoprecipitates. This improvement is consistent with Yb/Er enrichment within the nanoprecipitates, increasing their lattice mismatch with the matrix.