Abstract: Alloys containing the β/B2 phases of Ti-45Al-3Mo, Ti-45Al-3Mo-2Nb and Ti-45Al-5Mo were
prepared using an vacuum arc-melting machine. Heat-treatments were carried out at 1250 oC in an Ar
atmosphere. The temperature of 1250 oC is the temperature region of phase α + γ + (β/B2), and the heat
treatment condition which improves mechanical properties by decreasing the fraction of the β/B2 phase. The
presence of the β/B2 phase can result in relatively weakness at high temperatures and collapses the lamellar
structure of the α2 / γ phase during heat treatment. The transient oxidation behaviors of Ti-45Al-(3, 5)Mo-(2Nb)
(at%) alloys were investigated in an ambient atmosphere at 900 and 1000 oC. Initial oxidation behaviors and
oxidation resistance of the three alloys were compared at 1000 oC. The oxidation resistance of the Ti-45Al-
3Mo-2Nb alloy containing Mo and Nb was the most remarkable among the three alloys at 900 oC and 1000 °C.
At the same time, Si pack cementation coated Ti-45Al-3Mo-2Nb alloys and oxidation behavior were also
analyzed. The phase sequences of the multilayers of τ2 / Ti5Si4 / TiAl3 / TiAl2 /TiAl were observed on the
substrate. Also, a diffusion pathway of the silicide coating layers in the ternary phase diagram of Ti-Al-Si was
proposed. The oxidation resistance of the silicide coated TiAl alloys was improved during the oxidation tests
at 1000 oC.