DECAGONAL PHASES - NON-QUASI-CRYSTALLINE MICROCRYSTALLINE STATE IN AN AL-CU-CO-SI ALLOY

We present high-resolution electron microscopy and X-ray diffraction studies of the A & u. all Coy at room. temSperatur e. The sample is found periodic in one direction c and presents tenfold symmetry in the I = 0 diffraction plane perpendicular to this direction. The two complementary techniques show that the sample is not in a 2D quasi-crystalline state but in a microcrystalline state, which restores the overall tenfold symmetry in diffraction pattern. On the basis of our present results, we discuss some relationships that could exist between microcrystalline and quasi-crystalline phases. © 1990 IOP Publishing Ltd.