STUDY ON A DECAGONAL QUASI-CRYSTAL AND AN APPROXIMATE CRYSTALLINE PHASE IN AL70CO15NI10TB5 OBTAINED BY QUENCHING UNDER HIGH STATIC PRESSURE

A decagonal quasicrystal and a new crystalline approximant of the deca gonal quasicrystal have been found in Al70Co15Ni10Tb5 alloy, which was prepared by a method of quenching from the melt under a high static p ressure 7.0 GPa. The lattice parameters of the new crystalline approxi mant are a = 2.28 nm, b = 1.60 nm, c = 5.46 nm. A lattice image of the approximant was obtained by means of high-resolution electron microsc opy and was able to be regarded as an ordered pattern of Penrose tilin g, Based on the lattice image, a tiling model of the approximant was p ut forward.