Highly Ordered Icosahedral Quasicrystal of Al-Cu-Fe Alloy Studied by Electron Diffraction and High-Resolution Electron Microscopy

An icosahedral quasicrystal in a conventionally solidified Al-Cu-Fe alloy has been examined with electron diffraction and high-resolution electron microscopy. Diffraction and Kikuchi patterns taken with the incident beam exactly parallel to the 5- and 3-fold symmetry axes show strict 5- and 3-fold rotational symmetry. Any systematic shift of diffraction spots, which often appears in rapidly solidified quasicrystals, was not observed at all. A high-resolution electron micrograph taken with the incident beam parallel to the 5-fold axis shows no existence of phason strains in the icosahedral quasicrystal.