The Role of Borides in Near-γ Titanium Aluminides

This paper reviews how boride additions affect the microstructure, strength and creep properties of α2 + γ titanium aluminides. Important titanium boride structures in near-γ alloys include TiB2 and TiB; their structures and stability ranges are discussed first. Then, influences on matrix microstructure—grain refinement, enhanced microstructural conversion kinetics, and the stabilization of fine lamellar structure—are elaborated upon, for matrix microstructure plays the most important role in determining mechanical properties. The combined effects of reinforcement and microstructure on mechanical behavior are then explored, illustrating how the incorporation of grain refiners, such as titanium borides, facilitates thermomechanical processing and enables the tailoring of microstructure to optimize specific mechanical properties.