Powdered mixtures of CaO, ZrO2 and Al2O3 in various ratios were hot pressed. The mixtures reacted with titanium at 1600 °C for 30 min in argon to evaluate the suitable ceramic crucibles for casting of titanium. The interfacial microstructures between titanium and ceramic composites were characterized using X-ray diffrac-tometer, scanning and transmission electron microscope. The produced hot pressed mixtures that were chemically bonded together, contained calcium aluminate (CaAl2O4), calcium dialuminate (CaAl4O7), cubic zirconia (c-ZrO2), and calcium zirconium oxide (CaZrO3). The increase in Al2O3 amount led to the decrease in CaZrO3 amount and an increase in the amount of CaAl2O4, CaAl4O7 and c-ZrO2 due to the reaction of CaO and Al2O3. At the end of the reaction of the ceramic mixtures with Ti at 1600 °C for 30 min, the acicular α-Ti and β′-Ti were formed at the interface of Ti and the composites containing up to 10 vol.% Al2O3. In composites containing more than 20 vol.% Al2O3, Ti3Al5 was found at the interface instead of α-Ti and β′-Ti. Furthermore, CaZrO3, ZrO2 and Ca3Al2O6 existed on the sides of the ceramic far away from the interface. CaZrO3/Al2O3 composites with less than 20 vol.% Al2O3 could be a potential crucible or mould material for productive applications in titanium casting.
- Phase identification
- Titanium casting