Interreactions of TiAl3 Thin Film on Bulk γ-TiAl and on Bulk α2-Ti3Al Alloys at 700—1000°C

Interreactions of diffusion couples of TiAl3 film on bulk γ-TiAl and TiAl3 film on bulk α2-Ti3Al are investigated at high temperature. Experimental results show that TiAl2 layer and TiAl2/γ-TiAl mixed layers are observed at the interfaces of TiAl3 film/bulk γ-TiAl and TiAl3 film/bulk α2-Ti3Al diffusion couples, respectively, at 700∼1000°C. In addition, the growth rates of TiAl2 and γ-TiAl product layers comply well with a parabolic law. The growth activation energy, Qk, of the TiAl2 phase in the TiAl3 film/bulk γ-TiAl system is calculated as 158.9 kJ/mol, and Qk values of γ-TiAl and TiAl2 phases in TiAl3 film/bulk α2-Ti3Al system are 163.4 kJ/mol and 147.9 kJ/mol, respectively. These Qk values are similar in magnitude with those of TiAl3 phase formation in Ti-Al thin film diffusion systems. In this study, TiAl2 formation is suggested to have been nucleated at the interface during the heating prior to reaching the set temperature.