Composition Profiles within Al3Li and Al3Sc/Al3Li Nanoscale Precipitates in Aluminum

TL;DR

This study investigates the nanoscale composition and structure of Al3Li and Al3Sc/Al3Li precipitates in an aluminum alloy, revealing core-shell precipitate configurations and compositional variations that influence alloy strength.

Contribution

It provides detailed atom-probe tomography analysis of the composition profiles within Al3Li and Al3Sc/Al3Li precipitates, highlighting the formation of core-shell structures and compositional heterogeneity.

Findings

Presence of single-phase delta'-precipitates and core-shell alpha'/delta'-precipitates.

High strength conferred by precipitate structures with specific volume fractions.

Significant compositional variation in Li concentrations within precipitates.

Abstract

An Al-11.3Li-0.11Sc (at. %) alloy was double-aged to induce first alpha'-Al3Sc and then delta'-Al3Li precipitates. Atom-probe tomography revealed both single-phase delta'-precipitates and core-shell alpha'/delta'-precipitates (with respective average radii of 16 and 27 nm, and respective volume fractions of 12 and 9%) conferring a high strength to the alloy. Although the delta'-shells contain little Sc (~0.027 at. %), the alpha'-cores have a high Li content, with an average composition of Al0.72(Sc0.17 Li0.11). The Li concentrations within the delta'-phase and the Li interfacial excess at the delta'/alpha'-interface both exhibit wide precipitate-to-precipitate variations.