Interface interaction during the preparation of TiAl-(Nb, V) quaternary intermetallic single crystals by directional solidification based on Y2O3 doped BaZrO3/Al2O3 composite ceramic mold

In this work, a high-purity TiAl-(Nb, V) alloy single crystal rod with a size of 16 x 80 mm has been prepared by directional solidification in an Y2O3 doped BaZrO3/Al2O3 composite ceramic mold. The interface interaction between the alloy melt and mold is investigated, and the interaction mechanism is clarified. The results show that the reaction products of BaAl2O4 and small amounts of Ba5Y2ZrAl2O13, Ba3Al2O6 and Ba3ZrNb4O15 cover the refractory surface and thus effectively prevent further interaction. Two types of inclusions, i.e., (Al2_xYx)O3 and Ti5Si3 were confirmed in the single crystal and the number of inclusions are much less compared with other directionally solidified TiAl-based alloys prepared using Y2O3-coated Al2O3 and Al2O3 molds. Based on this, an interaction model is further constructed. The dissolution of the mold is controlled by oxygen diffusion from 0 to 1800 s, while by interface reactions from 1800 to 3000 s.