Münster 1997 – wissenschaftliches Programm
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M: Metallphysik
M 17: Amorphe und metastabile Metalle I
M 17.6: Vortrag
Donnerstag, 20. März 1997, 16:30–16:50, S 9
Containerless solidification of Zr-Cu-Al-Ni-Ti glass forming alloys = in a drop tube — •L.Q. Xing, G.P. G"orler, and D.M. Herlach — Institut f"ur Raumsimulation, Deutsche Forschungsanstalt f"= ur Luft– und Raumfahrt, 51140 K"oln
Droplets of the bulk glass forming alloy Zr57Cu20Al10Ni8Ti5
were containerlessly solidified during free fall in a drop-tube.
Particles with sizes ranging from 100 µ m to 1000 µ m were
produced and sorted into different size fractions by using proper meshes.
The solidified droplets were checked with respect to their amorphous state
by X-ray diffraction. The fraction of amorphous phase within the droplets
of various sizes was determined by measuring the heat of crystallization
in Differential Scanning Calorimetry (DSC) experiments. The heat of
crystallization of fully amorphous samples (cast in a copper mold) was
used as a reference. Since the droplet diameter correlates directly to the
reciprocal cooling rate, the critical cooling rates for glassy
solidification were obtained from these measurements. The glass forming
ability was studied in dependence of various heterogeneous nucleation
processes. It is shown that, e.g., heterogeneous ZrO nuclei lead to a
significant decrease of the glass forming ability.
L.Q. Xing
acknowledges financial support by the Alexander von Humboldt Foundation.