In this study, a Ti-40Al-10V alloy with quenching-tempering microstructure was prepared and was characterized by ultra-large β/B2 grains and submicrocrystalline γ laths within it. A definite Kurdjumov-Sachs orientation was identified between the β/B2 and γ phase. Isothermal compression tests were performed to examine the hot deformation behavior at various temperatures and strain rates. Based on the hyperbolic-sine equation, the deformation kinetics of the alloy were characterized by unexpectedly high activation energy (384 kJ/mol) and low stress exponent (2.25). For all the deformed samples, continuous dynamic recrystallization intensively occurred in the β matrix, accompanied by the simultaneous rotation of the γ laths. Moreover, a preferential orientation of <100>β
parallel to the compression axis was observed for β and γ phase, respectively. With the decreasing strain rates, the grain boundary/interface sliding gradually became prominent, which resulted in some superplastic deformation features, e.g., intensive strain-induced grain growth and interface migration, enhancing “wetting” of the γ grain boundaries, continuous weakening/vanishing of the local texture, etc. Meanwhile, the temperature played an insignificant role in the hot deformation behavior. The deformation mechanism was discussed in detail based on the microstructural observations and deformation kinetics.
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