Hydrogen induced softening mechanism in near alpha titanium alloy

Hydrogen induced softening mechanism in near alpha titanium alloy Ti600 (Ti-6.0Al-2.5Sn-4.0Zr-0.5Mo-0.4Si-0.1Y) is studied in this paper. The results show that, the hydrogenated alloy has a lower flow stress than the unhydrogenated alloy at the same temperature, and 0.3 wt.% is the optimum hydrogen content for Ti600 deformed at 850 °C. Compared with unhydrogenated Ti600 deformed at 950 °C, deformation resistance decreases by one third. A new method based on thermogravimetry analysis for studying dehydrogenation process of titanium alloys is proposed. The results demonstrate that with the addition of 0.3 wt.% hydrogen the phase transformation temperature decreases by around 100 °C. The reasons of hydrogen-induced softening are studied by XRD and TEM methods, which are attributed to the effects of hydrogen on the phase transformation, dislocation mobility, dynamic recovery and recrystallization during high temperature deformation process.