Berlin 2005 – wissenschaftliches Programm

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M: Metallphysik

M 27: Quasikristalle

M 27.1: Vortrag

Montag, 7. März 2005, 10:30–10:45, TU H111

Reversible Phase Transformation between amorphous and quasicrystalline state of ZrTiNiCu. — •S. Mechler, Ch. Abromeit, N. Wanderka, M.-P. Macht, G. Schumacher , B. Schattat, and S. Klaumuenzer — Hahn-Meitner Institut Berlin

During the crystallization process of several classes of metallic glasses quasicrystals are formed as the primary nucleating, intermediate phase. The alloy Zr_64.5Ti_11.4Cu_13.8Ni_10.3 can be produced by the splat quenching technique into amorphous sheets upto 50 µm thickness, whereas sheets of about 70-100 µm are fully quasicrystalline. Heating of the amorphous material leads at first to the transformation into the fully quasicrystalline state. The quasicrystals are metastable and vanish at higher temperatures in favor of crystalline phases. The phase transformations are investigated by means of DSC, XRD and TEM. To study the stability of quasicrystalline ZrTiCuNi under irradiation with swift heavy ions, we used Au, Xe and Kr ions in the energetic range of 300-600 MeV. Irradiation by 600 MeV Au, leads to full amorphization of the sample already for a fluence of 10¹³ /cm². At lower fluences, amorphous tracks inside the quasicrystals can be visualized by HRTEM. The amorphization of the quasicrystalline phase is ascribed to the high electronic energy loss of the Au ions (40 keV/nm). This state can be reversed again by heating.