Dresden 2003 – scientific programme
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M: Metallphysik
M 39: Flüssige und amorphe Metalle IV
M 39.4: Talk
Thursday, March 27, 2003, 12:30–12:45, IFW D
Formation of Quasicrystalline Phases by Crystallization of the Bulk Metallic Glass Zr46.75Ti8.25Ni10Cu7.5Be27.5 — •Stefan Mechler , Nelia Wanderka, and Michael-Peter Macht — Hahn-Meitner-Institut Berlin, Glienicker Str. 100, D-14109 Berlin, Germany
The bulk metallic glass Zr46.75Ti8.25Ni10Cu7.5Be27.5 (V4) is very stable against crystallization above the glass transistion (Tg= 603 K). Annealing of the as-quenched glass at 643 K for times longer than 5 h leads at first to the formation of icosahedral quasicrystals, which are an intermediate phase. When the annealing temperature is increased to 693 K, these quasicrystals can not be detected. Instead, several intermetallic phases are formed directly from the glass. When the V4 glass is annealed at 573 K for 6 weeks, a decomposition of the glass into two amorphous phases takes place. During further annealing of this pre-annealed glass at 643 K the icosaedral quasicrystals develop on a shorter time scale than in the as-quenched glass. In contrary to the as-quenched glass, annnealing of the pre-annealed glass at 693 K leads in the first stage to the formation of rather stable quasicrystals, which differ to the icosahedral ones. The influence of an annealing for different temperatures and times on the formation of quasicrystals is investigated by means of DSC, XRD, SEM and TEM.