STABLE AL-CU-CO DECAGONAL QUASI-CRYSTALS WITH DECAPRISMATIC SOLIDIFICATION MORPHOLOGY

A decaprismatic growth morphology has been found for the first time for the decagonal quasicrystal in the Al65Cu20Co15alloy slowly cooled from the melt.Substituting a little Si for A1 in this alloy, for example, Al62Si3Cu20Co15, results inquasicrystal decaprisms of 0-5 mm in diameter and several millimetres in length.These decaprisms showed possibly a 10/mmm morphology which was proved later byelectron and X-ray single crystal diffraction analyses. Moreover, the sharp selected-area electron diffraction (SAED) and convergent-beam electron diffraction (CBED)patterns show clearly a high degree of perfection and the X-ray precessionphotographs prove the single crystalline nature across a few millimetres of thisdecagonal quasicrystal. © 1990 Taylor & Francis Group, LLC.