Effect of hydrogen on the microstructural evolution of a γ-TiAl based alloy

The effect of hydrogen on the microstructural evolution of a Ti-46Al-2V-1Cr-0.3Ni (in at%) alloy deformed in temperature range 1323-1473 K and strain rate range 0.001-1 s−1 was investigated. The results show that the extent of lamellar decomposition is higher, and the microstructure is more homogeneous in the hydrogenated alloy than those in the unhydrogenated alloy. More recrystallized grains were observed in the hydrogenated alloy. Hydrogen-promoted lamellar decomposition is mainly attributed to hydrogen-induced lamellar bending, hydrogen-coarsened lamellae and hydrogen-promoted diffusion of elements. Lamellar decomposition, hydrogen-induced twinning and hydrogen-decreased stacking fault energy lead to more dynamic recrystallization. Hydrogen promotes α2-phase spheroidization and dynamic recovery, which are mainly attributed to hydrogen-promoted diffusion of elements and dislocation movement, respectively.