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Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 61: Liquid & Amorphous Metals I

MM 61.3: Talk

Thursday, March 14, 2013, 16:15–16:30, H26

Phase separation in ternary Co-Gd-Ti liquids — •Junhee Han1, Norbert Mattern1, Dirk Holland-Moritz2, Jozef Bednarcik3, Ivan Kaban1, Rafal Nowak4, Natalia Sobczak4, and Jürgen Eckert11IFW-Dresden, Dresden, Germany — 2Institut für Materialphysik im Weltraum, DLR, Köln, Germany — 3HASYLAB, DESY, Hamburg, Germany — 4Center for High Temperature Studies, Foundry Research Institute, Krakow, Poland

Phase equilibrium and solidification behavior of ternary Co-Gd-Ti (Co ≤ 35 at. %) alloys has been investigated by thermal analysis (DSC) and microstructural characterization of cast alloys (SEM/EDX). The phase equilibria with the liquid phase were studied in situ for two alloys Co30Gd35Ti35 and Co30Gd50Ti20 by combining electrostatic levitation of the melt with high-energy synchrotron X-ray diffraction at elevated temperature. For Co30Gd35Ti35 we observe two diffuse diffraction maxima (T = 1600 - 1700 K) giving direct evidence of liquid-liquid phase separation. The maxima positions exhibit a temperature dependent shift due to the change in chemical compositions with temperature in accordance with the binodal line. For Co30Gd50Ti20, no indication of phase separation is detected. Coarsened microstructures typically for phase separated liquids are observed in cast alloys Co30Gd35Ti35, Co25Gd37.5Ti37.5, Co10Gd45Ti45 and Co30Gd20Ti50. Our findings suggest that the stable miscibility gap of the binary Gd-Ti extends into the ternary Gd-Ti-Co system (up to Co < 35 at. %). Thermodynamic calculations of the ternary Co-Gd-Ti by the CALPHAD method are in a good agreement with experimental findings.

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