Abstract:The equiaxed γ grains and α2/γ laminas are the two main deformed microstructure of beta-gamma TiAl alloy. In this paper, mechanical properties and microstructural evolution of hot forged Ti-44Al-4Nb-4V-0.3Mo-Y alloy with equiaxed and lamellar microstructure were studied during high temperature tension. The results show that tensile temperature has a significant effect on the mechanical properties and microstructures of Ti-44Al-4Nb-4V-0.3Mo-Y alloy. At the same temperature, the tensile strength and yield strength of the TiAl alloy with equiaxed microstructure are slightly greater than those with lamellar structure，however the elongation difference is not significant. With the increase of tensile temperature, the tensile strength and yield strength of TiAl alloy decrease gradually, while the elongation increases significantly. For equiaxed microstructure， increasing tensile temperature, the equiaxed γ grains are elongated and complete dynamic recrystallization occurs to refine the microstructure of the TiAl alloy. For lamellar microstructure, the degree of decomposition of α2/γ laminas and recrystallization of γ laths increase with the increase of tensile temperature. The ductile brittle transition temperature of Ti-44Al-4Nb-4V-0.3Mo-Y alloy is between 750 ~ 800°C.