Effect of hydrogen on the β transus temperature of TC21 alloy

Effect of hydrogen on the β transus temperature of TC21 alloy was investigated by metallographic technique and dilatometry. It is found that the β transus temperature is closely related to the hydrogen content. For the hydrogenated TC21 alloy, the starting and finishing temperatures of α → β phase transition decrease with the increasing of hydrogen content before the hydride precipitates. And the finishing temperature of α → β phase transition increases as the hydrogen content increases after the hydride precipitates. Furthermore, corresponding inherent mechanisms of the above-mentioned phenomena have been presented according to atomic diffusivity, interface migration and the precipitation of hydride.

Research Highlights
► The β transus temperature of TC21 alloy is closely related to hydrogen content.
► The mechanism for effect of hydrogen on the β transus temperature is presented.
► Precipitation of hydride has a significant influence on the β transus temperature.
► The α/β interface migration has an important effect on the β transus temperature.
► The improvement of atom diffusivity affects the β transus temperature highly.