Abstract: The superlattice phase in Al-2.54Li-1.24Cu-1.01Mg-0.13Zr(AA8090) alloy have been studied by means of conventional transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), lattice image simulation and dynamical diffraction simulation. The research has testified the Silcock's model about the crystal structure of Al3Li and Al3Zr phases. It is discovered that Al3Li, AL3Zr and the co-precipitated Al3Li/AI3Zr phases exist simultaneously in the observed alloy. The co-precipitation of Al3Li/Al3Zr forms by that the Al3Li phase nucleates on and grows coherently around the Al3Zr phase. A further analysis predicts that the Al3Li phase precipitates by a spinodal decomposition process during water-quench; Whereas im the complex alloy, the nucleation of A13Li phase on the second-phase particle has played an important role on the formation of the superlattice phases.

Key words: Al-Li alloy, superlattice phases, high-resolution eletron microscopy