Guangyao Chen

Effect of CaO Additive on the Interfacial Reaction Between the BaZrO 3 Refractory and Titanium Enrichment Melt

The BaZrO3 and CaO-doped BaZrO3 ceramics were fabricated at 1750 ℃ for melting the Ti2Ni alloys, respectively. Employing XRD, OM and SEM, the influence of CaO on the composition of BaZrO3 and the interaction between the BaZrO3 ceramic and titanium alloy was investigated. The results showed that the CaO doped BaZrO3 was consisted of CaO and Ba1−xCaxZrO3. The grain on the surface of BaZrO3 ceramic was loose after melting, and the thermodynamic analysis indicated that the dissolution-erosion was responsible for the interaction mechanism. An amount of BaZrO3 refractory was attached to the Ti2Ni alloy bottom after the alloy was cooled. However, no refractory was found on the bottom of Ti2Ni alloy, which was cooled down on the CaO doped BaZrO3 ceramic. CaO additive can effectively reduce the interaction between the BaZrO3 refractory and the titanium melt, indicating that it was a very promising refractory for preparing the titanium alloy.

The Unidirectional Solidification of Ti-46Al-8Nb Alloy with BaZrO 3 Coated Al 2 O 3 Mould

The TiAl alloy with nominal composition of Ti-46Al-8Nb (at.%) is directionally solidified(DS) in a BaZrO3 coated Al2O3 mould with the certain withdrawing rates (120 μm/s), and the metal-BaZrO3 interface, microstructure and chemical composition of the alloy are evaluated. The result demonstrates that after the directional solidification a fully lamellar γ/α2 microstructure without BaZrO3 particles contamination is observed, and the BaZrO3 protective coating exhibits an effective barrier capability to avoid the direct contact between the mould base material and the TiA1 melt. The interface reaction between the mould and TiAl melt was analyzed by scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). The results showed that a certain thickness interface reaction layer is formed at the metal-mould interface with this withdrawing rate. And the reason may be the BaZrO3 coating is found to suffer some erosion and be slightly dissolved by the molten TiAl.