Regensburg 2004 – wissenschaftliches Programm
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M: Metallphysik
M 14: Flüssige und amorphe Metalle IV
M 14.1: Vortrag
Dienstag, 9. März 2004, 10:15–10:30, H6
Deformation-induced crystallization in amorphous Al88Y7Fe5 alloy — •Rainer Hebert1, Gerhard Wilde1, and John H. Perepezko2 — 1Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany — 2Department of Materials Science and Engineering, University of Wisconsin-Madison, 1509 University Ave., Madison, WI 53706, USA
Melt-spun amorphous Al88Y7Fe5 ribbons reveal a primary crystallization reaction of fcc-Al at 276C (heating rate: 20K/min). At room-temperature, primary crystallization of fcc-Al can be induced during intense deformation based on repeated cold-rolling and folding. The deformation-induced crystallization reaction is investigated based on XRD, TEM, SAXS and DSC analysis and discussed in light of nanocrystallization in shear-bands. The comparison between thermally-induced and mechanically-induced primary crystallization demonstrates that in terms of the size distributions for the Al-nanocrystals, both processing routes yield similar distributions, but the reaction pathways are different. Following annealing at 220C for 10min, the particle volume density in the rolled ribbons increases approximately one order of magnitude to about 1022m−3. Under the same annealing conditions, nanocrystals are not observed in the as-spun ribbon. The kinetics of the deformation-induced crystallization reaction is examined with the strain as a metric for the transformation. The experiments demonstrate that intense deformation of metallic glasses in combination with annealing offers the opportunity to catalyze higher nanocrystal densities than for annealing only, without adding additional elements to the alloy.