Development of ductile γ+α2 titanium aluminide through ingot metallurgy route, thermomechanical processing and characterization

The alloy is found to have predominantly two phases γ (TiAl) and α2 (Ti3Al) with moderately random texture and presence of small volume fraction of β-phase. Microstructure showed presence of varying width of α2+γ lamellar structure. Transmission electron microscopy (TEM) confirmed presence of extensive twinning, dislocations and stacking faults with two phase structure indicating twinning has played a significant role in deformation. Presence of minor amount of β phase has been found to be contributing factor for improvement in ductility. Fracture analysis shows failure was mainly by rupture of lamellar interfaces. Occasional deformation of lamellae is also noticed in the uniaxial tensile tested samples at intermediate strain rates of 10−3 s−1 and 10−2 s−1 wherever small increase in ductility is observed. Marginally lower ductility at lower strain rate is due to growth of microcracks at interlamellar sites of dissimilar orientation and at higher strain rate due to faster growth of microcracks at lamellae of similar orientation.