CRYSTALLINE SURFACE-LAYERS ON QUASI-CRYSTALS

Twin-related crystalline surface layer structures on Al-Li-Cu, Al-Cu-Fe icosahedral quasicrystals and rapidly solidified Al-Cu-Co decagonal quasicrystals have been studied, for the first time, by transmission electron microscopy. The structure of the surface layer is cubic with a lattice parameter of a = 0.29 nm and with a b.c.c. lattice in Al-Li-Cu and Al-Cu-Fe but a B2 structure in Al-Cu-Co. Interfacial misfit dislocations between the bulk quasicrystal and the surface layer have also been observed.