Investigations on cold deformation mechanisms of the hydrogenated Ti–6Al–4V alloys

The effect of hydrogen on the cold deformation behaviors of the Ti–6Al–4V alloys (α + β-type) has been investigated. By quenching from the β transition temperature a metastable microstructure is obtained. A pronounced influence of the addition of hydrogen on the deformation behaviors is found. Microstructures exhibiting large α″ martensites and metastable β phase show a better plasticity than that of the as-received alloy. It is shown that the cold deformation is controlled by the deformation twins and stress-induced martensitic transformation. The deformation twins appear inside the α″ martensite in specimens containing lower than 0.45 wt.% H, which promotes the deformation. When the hydrogen concentration is further increased up to 0.9 wt.%, the metastable β phases transform to α″ martensites during the deformation, which, together with the deformation twins, increase the true strain from 30% to 60%.