Effect of annealing on the microstructure of cast Ti-46Al-8Ta (at.%) alloy was evaluated at temperatures ranging from 700 to 800°C. Fine grain convoluted microstructure of heat treated alloy consisted of small lamellar colonies of α_2-Ti_3Al (crystal structure D0_(19)) intermetallic phase within γ-TiAl (crystal structure L1_0) phase. Annealing leads to precipitation of α_2 and τ (crystal structure B82) particles at the grain boundaries at the expense of theα_2 laths. This process is connected with a depletion of the grain boundaries of Ti and Ta and formation of Al rich γ phase. Lattice parameter a of the γ phase decreases, c increases and aspect ratio c/a increases with increasing time and temperature of ageing. The annealing leads to an increase of lattice parameters a and c and decrease of the aspect ratio c/a of both α_2 and τ phases.
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