Investigation of the interactions between titanium and calcium zirconium oxide (CaZrO3) ceramics modified with alumina

Abstract

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.