Al-Sc alloys, strengthened by nanoscale Al<sub>3</sub>Sc precipitates, exhibit coarsening and creep resistance up to 300 °C. By alloying with faster-diffusing Er and slower-diffusing Zr additions, complex core/double-shell precipitates are formed, with precipitates consisting of an Er-enriched core surrounded by a Sc- and Zr-enriched shells. These Al-Er-Sc-Zr alloys are stable against long-term coarsening at 400°C while exhibiting significant creep threshold stresses due to increased lattice parameter mismatch from Er additions.
The present study seeks ultimate strength and coarsening resistance by alloying Al-Er-Sc-Zr alloys with Group 5 additions (M = V, Nb, Ta), which are expected to be slower diffusers than Zr. By sequential nucleation of the constituent solutes we have engineered Al<sub>3</sub>(Er,Sc,Zr,M) precipitates with core/triple shell compositions. Relationships between the observed mechanical properties and the microstructural evolution during aging are established using transmission electron microscopy and atom-probe tomography.