Abstract
A decagonal phase which was grown from an icosahedral phase in a rapidly solidified Al 70 Pd 20 Mn 10 alloy by annealing at 800°C was examined by means of high-resolution electron microscopy. From the high-resolution image, we directly determined a two-dimensional arrangement of atom clusters, which are structural units of the Al–Pd–Mn decagonal quasicrystal, in a wide region of about 100 ×100 nm 2 . The main part of the observed area shows a highly ordered decagonal quasicrystal with weak linear phason strain. A tiling constructed by connecting the atom clusters with lines was compared with theoretical tilings.