Influence of Ta Doping on Microstructure and Mechanical Properties of γ-TiAl Based Alloy

The evolution behavior of massive γ (γ_m) quenching from single α-phase region in Ti-48Al-2Nb-2Cr-xTa (x=0, 1.0, 2.0) alloy is systematically studied. The electron back scattering diffraction method is used to character the grain orientation. The precipitation of γ_m phase can be greatly promoted by Ta element. The critical content of Ta, promoting or inhibiting the precipitation of γ_m, is 2% (atom fraction). Ta element can refine the γ_m subgrains, and the various γ_m variants can directly nucleate inside the α₂ grains in the form of BOR. In the course of growth, the γ_m nuclei selects its variant over the close-packed 111γ plane, making the γ_m nuclei deviating from BOR.