Combined influence of strain rate and hydrogen on the deformation behavior of a near-α titanium alloy

The deformation behavior of the near-α titanium alloy Ti–6Al–3Nb–2Zr–1Mo, containing 20–210 ppm hydrogen and tested at strain rates of 10⁻⁵–10⁻¹ s⁻¹, has been investigated by conducting tensile testing and microstructural characterization. The results show that at strain rates ≤10⁻³ s⁻¹, increasing hydrogen concentration improves ductility, while it deteriorates ductility at higher strain rates. The change in ductility with increasing strain rate remains relatively small at strain rates ≤10⁻³ s⁻¹ for all hydrogen concentrations, but at higher strain rates, an increase in strain rate results in a decrease in ductility. Additionally, the addition of hydrogen has little effect on the strain rate sensitivity and work hardening exponent. The detrimental effect of hydrogen addition on ductility at strain rates >10⁻³ s⁻¹ can be attributed to the enhanced strain localization caused by the presence of hydrogen. In cases of lower strain rates, the increase of ductility with the addition of hydrogen is due to the promotion effect of hydrogen on dislocation mobility.