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MM: Metall- und Materialphysik

MM 28: Amorphous and Liquid Materials III

MM 28.3: Talk

Thursday, March 30, 2006, 12:15–12:30, IFW B

Microstructure and thermal behavior of Ni-Nb-Y alloys with additions of Sn and B — •Uwe Siegel, Uta Kühn, Norbert Mattern, Annett Gebert, and Ludwig Schultz — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany

Ni-Nb-Y alloys with additions of Sn and B were prepared by melt-spinning and copper mold casting technique to achieve different cooling rates. The microstructure of the samples were investigated by means of X-ray diffraction and SEM and the thermal behavior was analysed by DSC measurements. The Ni_58.5Nb_20.25Y_21.25 alloy is known for its two phase amorphous microstructure obtained by rapid quenching [1]. Lower cooling rates, e.g. copper mold casting of this alloy, lead to a fully crystalline structure. Additions of Sn and B usually increase the glass forming ability of the Ni-Nb alloy system [2]. Based on these results the two-amorphous phase alloy was modified with different Sn and/or B contents in order to increase the glass forming ability and, therefore, to obtain bulk samples with a two amorphous phase microstructure. However, for the specific alloy composition, witch also contains Y, the formation of solid solutions is favoured what results in the precipitation of different crystalline phases during the solidification process at lower cooling rates. In contrast, using the melt spinning technique, decomposition of the amorphous phase was also obtained for Ni-Nb-Y-Sn alloys.

[1] Mattern, N. Kühn, U., Gebert, A., Gemming, T., Zinkevitch, M., Wendrock, H., and Schultz, L., Scripta Mater. 53, 271 (2005). [2] Choi-Yim, H., Xu, D. H., and Johnson, W. L., Appl. Phys. Lett. 82(7), 1030 (2003)