Microstructure and mechanical properties of TiAl-based alloy

Two phases gamma titanium aluminide alloy, Ti-46.5Al-2.5V-1Cr, was investigated to characterize microstructures and to define the microstructure/ mechanical property relationship. Many kinds of microstructure of gamma and α2, phases were obtained by heat treatments in the α+γ, α2+γ and α fields. The effects of microstructure on tensile properties, fracture toughness and J-R resistance curve at room temperature, were systematically studied. The experimental results showed that the microstructure had a strong effect on mechanical properties. The duplex microstructure produced by heat treatment at 1250°C × 4 h with controlled cooling resulted in the highest ductility of 4.8% tensile elongation, low fracture toughness and crack growth resistance. The fully lamellar microstructure produced by heat treatment in the α field having large grain sizes resulted in the highest fracture toughness but the lowest ductility.