| Abstract Scope |
Al-Sc alloys are strengthened by nanoscale Al<sub>3</sub>Sc precipitates (L1<sub>2</sub> structure). By alloying with faster-diffusing Er and slower-diffusing Zr additions, core/shell precipitates are formed, consisting of an Er-enriched core surrounded by a Zr-enriched shell that enhances strength and thermal stability, respectively. 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 precipitate sizes, volume fraction, number density, and compositions are established using atom-probe tomography throughout the microstructural evolution of the alloys. |