Berlin 2005 – wissenschaftliches Programm
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M: Metallphysik
M 12: Flüssige und amorphe Metalle III
M 12.5: Vortrag
Freitag, 4. März 2005, 15:45–16:00, TU H111
Modification of the crystallization sequence of amorphous Al 88Y7Fe5 — •Nancy Boucharat, Harald Rösner, and Gerhard Wilde — Institute of Nanotechnology, Research Center Karlsruhe, P.O.B. 3640, D-76021 Karlsruhe, Germany
Al-rich glassy alloys have attracted extensive attention due to their thermal stability against crystallization, since upon heating a high number density of Al-nanocrystals can develop in a residual amorphous matrix. One of the intriguing challenges is the understanding of the kinetics involved in the crystallization process since the retention of high number densities of nanocrystals is not completely understood. Calorimetric and structural analyses of glassy Al88Y7Fe5 have been performed after thermal treatments at temperatures well below the glass transition and after the incorporation of different immiscible elements, i.e. Pb and In into the melt prior to quenching. The results indicate clearly that the primary crystallization reaction can be markedly influenced with the addition of 1 at.% In or Pb. The impact of incorporated particles is examined on the basis of heterogeneous nucleation concepts that account for the microstructure changes. Additionally, it is shown that by modifying the concentration gradient that forms at the interface of growing Al-nanocrystals the nucleation of a new metastable ordered phase can be controlled. Support by the DFG is gratefully acknowledged.