Al-Cu-Co-Ge SINGLE DECAGONAL QUASICRYSTALS GROWTH BY DIRECTIONAL SOLIDIFICATION

The large single decagonal quasicrystals of 0.8 mm in diameter and 10 mm in length in Al-Cu-Co-Ge alloy have been obtained by controlled unidirectional solidification.In the process of growth, all of the single quasicrystals grew preferentially along uni-orientation of solidification.The centre axis of quasicrystalline prisms is the tenfold rotational symmetry axis. Under the condition of temperature gradient about 95℃/ cm,the segregation will be occurred and the growing interface will be changed from planar structure into cellular and/ or dendritic one with increasing directional solidification rate.and a large number of crystalline phases will be produced. Thus,it seems to be no means of growing required single quasicrystals of high quality.