Variant selection of massive γ subgrains and corresponding mechanical properties in Ta containing γ-TiAl-based alloys

The variant selection of subgrains in massive γ (γ_m) is systematically studied by 0–2 at.% Ta-containing γ-TiAl-based alloy. Results show that the precipitation of γ_m phase increases first, and then decreases with the rising of Ta. The critical content of Ta, which massive transformation is promoted or inhibited, is identified. EBSD and HRTEM results reveal variant selection process during nucleation and growth inner α matrix along all possible {1 1 1}γ, in terms of minimization of energy of highly defected α grain caused by Ta, thereafter, the subgrains of γ_m are refined. These fine subgrains and highly defected α₂ grain can enhance the mechanical properties of TiAl-xTa alloy.