Regensburg 2002 – wissenschaftliches Programm

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M: Metallphysik

M 12: Amorphe und metastabile Metalle III

M 12.3: Fachvortrag

Dienstag, 12. März 2002, 15:00–15:15, H4

In-situ Observation of Phase Transformations of Amorphous Fe-Cr-Mo-Ga-P-C-B Alloy Using Synchrotron Radiation — •M. Stoica¹, J. Eckert¹, S. Roth¹, L. Schultz¹, A.R. Yavari², and A. Kvick³ — ¹I.F.W. Dresden, Postfach 270016, D-01171 Dresden — ²LTPCM, INP Grenoble, BP75, 38402, St-Martin-d’Heres Campus, France — ³ESRF, 38042 Grenoble, France

Starting with the composition Fe_65.5Cr₄Mo₄Ga₄P₁₂C₅B_5.5, we prepared amorphous rods with different diameters, between 1.5 and 3 mm. The phase transformations during heating and subsequent cooling from the melt were observed by in-situ X-ray diffraction measurements in transmission configuration, using a high intensity high-energy monochromatic (0.01304 nm) synchrotron beam at the ESRF Grenoble. The samples were heated up to the melting point and cooled down with acquisition of X-ray patterns at each 2s during heating and during cooling. After the fast heating with 5 K/s, the alloy became fully crystalline, and the crystallization of the amorphous phase occurs via the formation of a metastable intermediate phase. The cooling rate from the molten state was around 20 K/s, i.e. not sufficient to retain an amorphous phase. The phases observed in the crystalline state obtained by heating do not correspond to those occurring after cooling.