Composition profiles within Al3Li and Al3Sc/Al3Li nanoscale precipitates in aluminum

An Al - 11.3Li - 0.11Sc ( at. % ) alloy was double aged to induce first alpha' - Al(3)Sc and then delta' - Al(3)Li 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 ( similar to 0.027 at. % ), the alpha' - cores have a high Li content, with an average composition of Al(0.72) ( Sc(0.17)Li(0.11) ). The Li concentrations within the delta' - phase and the Li interfacial excess at the delta' / alpha'- interface both exhibit wide precipitate- to- precipitate variations. (C) 2008 American Institute of Physics.