Formation of Quasicrystals In Ti-Zr-Ni Alloys

초록

Since the first discovery of 5-fold rotational symmetry in a rapidly quenched Al-Mn alloy in 1984, Ti-based quasicrystals are widely studied in the condensed matter physics and materials science fields because of their unique property showing a 5-fold sharp diffraction pattern which is theoretically forbidden in physics. Starting with TiZrNi alloys with initial compositions of 45, 38, and 17 for Ti,, Ar, Ni, respectly, that are known to relatively easy to form quasicrystals by rapid quenching method, we prepared samples with compositions of Ti from 33 to 50 at.% fixing the Ni concentration. Ti-Zr-Ni alloys were prepared by an arc-melting method on the Cu-hearth in an Ar atmosphere, and were subsequently quenched on a rotating stainless still wheel (1000~3000 revolution per minute) producing the metallic ribbons (about 20μm thick). Structures of the samples were analyzed by using an X-ray diffraction (XRD) and a transmission electron microscopy (TEM). The samples prepared by this method showed various structures from C-14 Laves phase (hcp) to amorphous, and quasicrystals. Interestingly, Ti50Zr33Ni17 alloys formed the phase pure quasicrystals when they were rapidly quenched. Our results strongly supports that Ti-based quasicrystas are formed in a wide range of compositions.