Interfacial reactions between titanium–copper melt and crucible oxides

Interfacial reactions of various cold isostatic pressed oxide crucibles (calcia, yttria-stabilized zirconia, and yttria) with Ti–5wt% Cu alloy at 1680 °C for 15 min melting in an argon environment have been investigated to estimate the corrosion resistance. Predicting thermodynamic analysis results indicate that oxide refractories based on calcia, zirconia, and yttria, can be used for melting titanium–copper alloy. However, significant differences between experimental results and those thermodynamic analysis results in the ZrO2–12 wt% Y2O3 and CaO systems were identified. The surface observations and element distribution made on cross-sections perpendicular to the interface using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) show that obvious interfacial reactions between alloy melt and ceramics in ZrO2–12 wt% Y2O3, and CaO systems occur at experimental temperature, while yttria shows the most superior stability with the most desirable features of interface properties of metal and crucible, and the product of dissolved Y2O3 was still found in the metal. Meanwhile, the interaction between the ZrO2 oxide and the Ti–5 wt% Cu melt can be effectively reduced by the addition of Y2O3. The high apparent porosity of the crucible results in low resistance to erosion caused by Ti–5Cu melt. Moreover, the reduction of calcia causes the boiling of the melt. These results would provide the basis for designing a new refractory for the melting of titanium–copper alloy.