Investigation of hydrogen influencing γ-phase true and pseudo twinning in a TiAl based alloy during high-temperature plane strain compression

In this paper, the effect of hydrogen on true and pseudo twinning of γ phase in a TiAl based alloy was investigated by means of plane strain compression tests at elevated temperature. The results showed that hydrogen could increase true- and pseudo-twin boundaries of γ phase. Hydrogen-decreased stacking fault energy, hydrogen-promoted Shockley dislocation movement, hydrogen-decreased stacking fault energy and hydrogen-enhanced element diffusion promoted γ-phase mechanical twinning and grain boundary migration. Furthermore, more γ-phase mechanical twinning and grain boundary migration led to more true-twin boundaries. Additionally, hydrogen could promote order twinning. The interaction between true- and order-twin boundaries cloud result in pseudo-twin boundaries. Therefore, hydrogen-promoted true and order twinning could indirectly increase pseudo twinning.