Introduction of Surface Defects in the γ Phase Improves the Mechanical Properties of TiAl Alloys

Actively introducing different types of defects into γ phase is an effective means to improve the mechanical properties of TiAl alloys at high temperatures. Ta was added in Ti-47Al-6Nb-0.1C alloy, and defect types, microstructure, mechanical properties at high temperatures, and related mechanisms of the alloy were studied. Results show that stacking faults (SFs), twin boundaries (TB) and 120° rotation boundaries (RB) are formed in the γ phase between lamellar colonies after adding Ta. Ta promote the generation of SFs and RB by reducing the stacking fault energy and RB formation energy. SF continuously generates and forms nanotwins. The tensile strength and elongation of the alloy at 900 ℃ reach 520.2 MPa and 9.4 %, respectively. TB and RB hinder dislocation slip. SFs decompose dislocations to consume their energy.