X-ray and TEM studies of Al-Fe-Cu dodecahedral particles : characterization of their microcrystalline state of pseudo-icosahedral symmetry

Abstract

Dodecahedral particles of Al-Fe-Cu alloy, obtained by slow solidification, have been studied by X-ray diffraction and transmission electron microscopy. Their peculiar microcrystalline structure of overall pseudo-icosahedral symmetry, previously identified by high resolution imaging and electron diffraction, is shown to be conformed by indexing of X-ray precession patterns. The crystal system is rhombohedral with cell parameters a = 32.16 Å and α = 36°. The space tiling problem of mean perfect icosahedral order, using only one rhombohedral cell, is discussed on the basis of some preliminary investigations in high resolution electron microscopy.