Interrupted Oxidation Kinetics of the TiAl Alloys in Static Air

The interrupted oxidation behaviours of five kinds of as-cast TiAl alloys at 700°C∼1 000°C in static air have been investigated using thermogravimetric analysis (TGA). The results show that the oxidation of the TiAl alloys at 700°C for 100 h is slight, and the interrupted oxidation kinetic curves of the TiAl alloys at 800 C ∼ 1 000 C for 100 h can be described by a power function (ΔMⁿ = k_nl, where 1≤n≤2 normally), indicating that the interrupted oxidation curves of the TiAl alloys lie in between linear and parabolic ones. Alloying constituents of the TiAl alloys remarkably influence the oxidation behaviour at middle and high temperatures (for example 900 C), while the differences between the oxidation behaviours of the five TiAl-based alloys studied become smaller as the oxidizing temperature increases further (for example up to 1 000°C). The oxidation resistance of binary TiAl alloys is better than that of ternary TiAl-Cr alloys. The oxide layers spall off when TiAl alloys oxidize at high temperature or for long times, thereby causing the oxidation to accelerate.