Microstructural evolution of hot-forged high Nb containing TiAl alloy during high temperature tension

Microstructural evolution of the as-forged Ti-44Al-8Nb-0.2W-0.2B-Y alloy during high temperature tensile tests between 650 and 950 °C, at strain rates of 1×10⁻⁴ s⁻¹, 2×10⁻⁴ s⁻¹ and 5×10⁻⁴ s⁻¹, is investigated in this study. Tensile properties of the alloy are extremely sensitive to the test temperature and strain rate. At a strain rate of 5×10⁻⁴ s⁻¹, ductile-brittle transition temperature (DBTT) of this alloy is between 750 and 800 °C. At lower temperatures, the principal deformation mechanism involves breaking down of remnant lamellar structure and deformation of twins. Above 900 °C, dynamic recrystallization (DRX) occurs and the extent of DRX improves with an increase in temperature and strain as well as a decrease in strain rate. Under specific test conditions, the ω phase forms by the solid-state phase transformation: α₂→γ+ω. The inhomogeneous microstructure remarkably influences the mechanical properties of the hot-forged pancake.