Core/Shell Precipitates in Al-Li-Sc-Zr Alloys.

V. RADMILOVIC; M. D. ROSSELL; A. TOLLEY; E. MARQUIS; R. ERNI; U. DAHMEN

Aachen, Alemania

Conferencia; 14th European Microscopy Congress,; 2008

Recent work on AlScZr alloys has shown that a precipitate core-shell structure may be responsible for the modification of properties in a precipitate-hardened alloy system. It was demonstrated that the precipitates contained Sc and Zr, but that the distribution of Zr was not homogeneous. Instead, a Zr rich shell surrounded an Al3Sc core, acting as a diffusion barrier that reduced the growth rate of the Sc rich core.In this work we investigate the effct of Li addition to AlScZr alloys on core-shell precipitate formation. The role of Li as a transient nucleating agent for Sc and Zr during heating and the formation of an Al3Li shell around (Sc.Zr) rich precipitates during cooling is documented using atom probe tomography (APT) and energy filered electron microscopy (EFTEM), high angle annular dark field imaging (HAADF) as well as high resolution transmission electron microscopy (HREM).