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

• The critical content of Ta which massive transformation is promoted or inhibited is 2 at.%. • Variant selection of γ m inner α matrix makes second generation γ m deviate from BOR. • Refinement of γ m and high density of defects in α 2 enhance the mechanical properties. 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 α 2 grain can enhance the mechanical properties of TiAl-xTa alloy. [ABSTRACT FROM AUTHOR]