Gd-Ti is a basic system for synthesis of special materials for magnetic applications such as Gd-Co-Ti, Gd-Fe-Ti, Gd-Mn-Ti and Gd-Ni-Ti alloys. These materials are usually produced using liquid-assisted processes. Therefore, knowledge of thermodynamic and thermophysical properties of molten Gd-Ti alloys is of high scientific interest and practical importance. If the measurements in the solid state are relatively simple, investigations of Gd-Ti melts is extremely difficult task. The problem is not with the high melting temperature, but rather with the high chemical aggressiveness of molten Gd and Ti against industrially available ceramic crucibles.
We have studied the behavior of liquid Gd-Ti alloys on Al2O2, Y2O3 and ZrO2 ceramics in a wide temperature range (up to 1600 °C) under flowing protective gas (Ar) by the sessile drop technique using both contact heating and non-contact heating procedures. Due to the use of a high-speed high-resolution CCD camera it was possible not only to record wetting behaviour and interactions of the melts with ceramic substrates but also to observe in real time the phase transformations in the Gd-Ti alloys upon heating and cooling through the liquid-liquid miscibility gap.
The eutectic and monotectic transformations determined in this study show a good agreement with the results of recent X-ray diffraction investigations of the solid and liquid Gd-Ti alloys. The microstructure of solidified sessile drop samples has been investigated by X-ray computed tomography. The interfaces between Gd-Ti alloys and ceramics have been studied by scanning electron microscopy combined with energy-dispersive X-ray spectrometry. The results of these investigations will be presented.
Acknoledgment: The research has been carried out in the frame of German-Polish collaboration program with partial financial support from Deutscher Akademischer Austausch Dienst (Project No. DAAD50755060) and the Ministry of Science and Higher Education of Poland (Project #002/2011/2012)