Tailoring a Dual-Scale Heterostructure With γ-Textures and Nano-β₀ Dispersion for Synergistic Enhancement of Mechanical Properties of TiAl Alloy

The limited crack resistance of coarse grain boundaries and coarse interfaces leads to an incompatibility between high-temperature strength and ductility in TiAl alloys. Tailoring stress-oriented textures and multiscale heterogeneous interfaces can effectively impede crack propagation, thereby overcoming this trade-off. In this study, a novel dual-scale three-phase heterogeneous microstructure was developed through thermomechanical processing, enabling synergistic regulation of texture and interface characteristics. The resulting microstructure is composed of micrometer-scale equiaxed γ phase, equiaxed α₂ phase, and nanoscale equiaxed β₀ phase. At room temperature, this microstructure exhibits higher fracture toughness and better crack resistance than the coarse lamellar colony microstructure. At 900°C, tensile strength comparable to that of the initial lamellar is retained, whereas elongation is increased by a factor of five. The retained strength is attributed to the combined effects of texture strengthening from equiaxed γ phases and dispersion strengthening from nano-β₀ precipitates. The enhanced plasticity arises from the activation of multiple slip systems within the γ textures and stress dissipation at the nano-γ/β₀ interfaces. This study establishes a microstructural design strategy that simultaneously exploits texture, phase distribution, and nano-precipitation, providing a viable pathway for the design of TiAl alloys with superior mechanical properties under high-temperature service conditions.