Ordered γ-brass structures coexisting with the decagonal quasicrystal in a Ga46Fe23Cu23Si8 alloy

In a moderately rapidly solidified Ga,,Fe,,Cu,,Si, alloy, a face-centered-cubic (fcc) superstructure (a = 1.78 nm) and a hexagonal superstructure (a(hex) = 2.18 nm and c(hex) = 0.77 nm), based on the same body-centered-cubic (bcc) gamma-brass structure (a = 0.89 nm), were found-by means of micro-area electron diffraction-to coexist with the decagonal quasicrystal. The fee superstructure is probably similar to one of the F-centered-gamma-brass structure and has a parallel orientation relationship with the bcc fundamental structure. The hexagonal superstructure has its (001) parallel to the (11(1) over bar) of the bcc gamma-brass structure and its c(hex) = a(bcc)[11(1) over bar]/2, and their lattice correspondence relationship has been derived. Electron diffraction evidence is presented to show that these two superstructures are possibly crystalline approximants of the decagonal quasicrystal.