Affiliation: | aDepartment of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208-3108, USA bRockwell Scientific, 1049 Camino Dos Rios, Thousand Oaks, CA 91360, USA cAlcoa Inc., Alcoa Technical Center, Alcoa Ctr., PA 15069, USA |
Abstract: | Atom-probe tomography (APT) and high-resolution transmission electron microscopy are used to study the chemical composition and nanostructural temporal evolution of Al3(Sc1−xZrx) precipitates in an Al–0.09 Sc–0.047 Zr at.% alloy aged at 300 °C. Concentration profiles, via APT, reveal that Sc and Zr partition to Al3(Sc1−xZrx) precipitates and Zr segregates concomitantly to the -Al/Al3(Sc1−xZrx) interface. The Zr concentration in the precipitates increases with increasing aging time, reaching a maximum value of 1.5 at.% at 576 h. The relative Gibbsian interfacial excess of Zr, with respect to Al and Sc, reaches a maximum value of 1.24 ± 0.62 atoms nm−2 after 2412 h. The temporal evolution of Al3(Sc1−xZrx) precipitates is determined by measuring the time dependence of the depletion of the matrix supersaturation of Sc and Zr. The time dependency of the supersaturation of Zr does not follow the asymptotic t−1/3 law while that of Sc does, indicating that a quasi-stationary state is not achieved for both Sc and Zr. |