Ordered γ-brass structures coexisting with the decagonal quasicrystal in a Ga_46Fe_23Cu_23Si_8 alloy

摘要

In a moderately rapidly solidified Ga_46Fe_23Cu_23Si_8 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) γ-brass structure (a = 0.89 nm), were fund-by means of micro-area electron diffraction--to coexist with the decagonal quasicrystal. The fcc superstructure is probably similar to one of the F-centered-γ-brass structure and has a parallel orientation relationship with the bcc fundamental structure. The hexagonal superstructure has its (001) parallel to the (l1l) of the bcc γ-brass structure and its c_hex = a_bcc[lll]/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.