Dresden 2006 – wissenschaftliches Programm
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MM: Metall- und Materialphysik
MM 20: Amorphous and Liquid Materials I
MM 20.3: Vortrag
Dienstag, 28. März 2006, 15:15–15:30, IFW D
The Origin Of Glass Forming Ability in Zr-Ti-Ni-Cu-Be Bulk Glasses — •S. Mechler, M.-P. Macht, and N. Wanderka — Hahn-Meitner Institut-Berlin, Glienicker Str. 100, 14109 Berlin
Zr46.8Ti8.2Ni10Cu7.5Be27.5(V4) is one of the best metallic glass formers known so far. This glass exhibits an extended supercooled liquid region. At temperatures above the glass transition it can form a quasicrystalline phase. The quasicrystals are found to be mainly depleted in Be and enriched in Ti. A series of alloys based on V4 composition with variation of Be content (from 0 to 35 at.%) were produced in order to investigate the influence of the Be on the glass forming ability (GFA). The Be-free glass shows only a narrow temperature region between glass transition and crystallization. After heat treatment around the glass temperature it shows a polymorphous transition from the amorphous to the quasicrystallline state. Higher Be contents result in better GFA. The GFA has its maximum for the alloys with Be contents between 25 at.% and 27.5 at.%. During annealing of these alloys the formation of the quasicrystalline phase is retarded. Upon heating in DSC the crystallization is shifted to higher temperatures, leading to the observed large temperature range between glass transition and crystallization of V4 glass. Investigations of the short range order in the glasses with different Be content indicated correlation between Icoshedral Short Range Order (ISRO) and Be content, with a highest degree of ISRO in the Be-free alloy. It is concluded that the ISRO is the key parameter in understanding the bulk glass forming ability and the extended stability of the supercooled liquid in the Zr-Ti-Ni-Cu-Be system.