Hot tensile behavior of a TiAl alloy with a (β0 + γ) microduplex microstructure prepared simply by heat treatments

A (beta(0) + gamma) microduplex microstructure was prepared in a Ti-42Al-8.5V (at%) alloy by means of quenching-tempering treatments, which was characterized by ultra-fine gamma platelets embedded in millimeter-sized beta(0) grains according to a definite K-S orientation relationship. Hot tensile tests were performed at 850-1000 degrees C with strain rates of 5 x 10(-4)-5 x 10(-3) s(-1) and a near-superplastic creep behavior was yielded. As a consequence, high elongations (>100%) were obtained with a stress exponent of similar to 3. Deformation mechanism was further analyzed by examining the microstructure and orientation evolution in individual beta(0) grains. The results showed that significant crystal rotation and fragmentation occurred in beta(0) matrix due to plastic flow and recrystallization, leading to an equiaxed grain structure with a weak preferential orientation resembling ND fiber where {111}< 112 > was the dominant component. In contrast, evident globularization/coarsening of the gamma platelets was observed during deformation. Meanwhile, the gamma platelets were slightly deformed but drifted with the p o matrix. The spontaneous rotation due to grain boundary/interface sliding resulted in dramatic orientation divergence of gamma phase. A weak and unusual < 110 > fiber was produced due to the preservation of K-S orientation relationship. (C) 2021 Elsevier B.V. All rights reserved.