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In this paper, we study the effect of the hydrogen presence in a solid solution on the stability of the structural and phase state and the mechanical properties of the ultrafine-grained titanium alloy of the Ti-Al-V-Mo system (VT16 grade) in the temperature range of 573–973 K in a vacuum and air. It was established that during annealing under conditions of hydrogen degassing from the ultrafine-grained structure, a β → α″ → α phase transformation and redistribution of alloying elements are observed, which contribute to the formation of a thin-plate (α + α″ + β) structure in β grains and an increase in the mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

Hydrogen effect on the deformation behaviour of the ultrafine-grained titanium alloy (VT16 grade) is studied at the temperature interval (293–973) K. Hydrogenation to the concentration of 0.3 wt % is found to lead to an increase in the values of uniform deformation and total deformation to failure at temperatures 293–573 K. In the range of higher temperatures (673–973) K, hydrogen presence reduces the resistance of the ultrafine-grained VT16 alloy to the localization of deformation at the macro-level and value of deformation to failure. Possible reasons for the increase in the transition temperature of the ultrafine-grained VT16 alloy to the superplastic state and the decrease in the temperature interval of the manifestation of its superplastic properties in the presence of hydrogen in a solid solution are discussed. [ABSTRACT FROM AUTHOR]