Influence of elevated temperature on hydride formation and hydrogen-assisted deformation in pure titanium

The effect of temperature on hydride formation and hydrogen-induced deformation in α-Ti was investigated using tensile testing combined with in-situ SEM observations. Microstructural characterization of hydrogen-charged and deformed specimens at both room temperature and 80 °C demonstrates that temperature significantly alters both the hydride phase and the mechanical response of the α-Ti matrix. Charging at 80 °C produced a more extensive surface hydride layer and a distributed subsurface hydride morphology while suppressing subsurface twinning. During testing at 80 °C, pronounced surface cracking and cleavage of hydrides were markedly reduced, despite reductions in apparent yield stress and uniform elongation, together with increased microvoid formation. These observations are consistent with a greater contribution of hydrogen in solid solution and increased ductility of hydrides at elevated temperature. The apparent specimen response therefore shifts from surface cracking and constrained deformation associated with hydrides at room temperature toward localized, dislocation-mediated deformation at 80 °C. At elevated temperature, the response is governed by competition between enhanced dislocation nucleation, which promotes earlier plastic deformation, and the constraining effects of the external hydride layer and distributed hydrides on subsequent plastic flow. These findings establish a mechanistic framework linking temperature, hydrogen state, and deformation behavior in α-Ti.