Effect of hydrogen on the structural and phase state of the fine- and ultrafine-grained structure of two-phase (alpha + beta) titanium Ti-6Al-4V alloy was investigated by the methods of electron microscopy and X-ray diffraction analysis. The defect structure of the fine- and ultrafine-grained samples before and after hydrogen treatment was studied by the implemented Positron lifetime technique. Hydrogenation is found to result in minor structural and phase changes both in fine- and ultrafine-grained samples
