Formation of Al–Y oxide during processing of γ-TiAl

While processing Y₂O₃ dispersed γ-TiAl, Y₂O₃ particles which dissolved during hot isostatic pressing (HIP’ing) were found to precipitate during the heat treatment in the form of a mixed Al–Y oxide. To understand the chemical reaction that occurs between Y₂O₃ and γ-TiAl during the heat treatment cycle, a powder mixture comprising of γ-TiAl and 10 wt.% Y₂O₃ was mechanically alloyed (MA’d) for 8 h and the milled powder was subjected to differential thermal analysis (DTA) at 1150 °C prior to analyzing it using X-ray diffraction technique. The present study clearly demonstrates that aluminum in the combined form either as γ-TiAl or Al₂O₃ reacts in a similar manner with Y₂O₃ when milled and heat treated at 1150 °C. In either case there is formation of Al₂Y₄O₉ (2Y₂O₃.Al₂O₃).