Formation mechanism of hydride precipitation in commercially pure titanium

Since titanium has high affinity for hydrogen and reacts reversibly with hydrogen, the precipitation of titanium hydrides in titanium and its alloys cannot be ignored. Two most common hydride precipitates in alpha-Ti matrix are gamma-hydride and delta-hydride, however their mechanisms for precipitation are still unclear. In the present study, we find that both gamma-hydride and delta-hydride phases with different specific orientations were randomly precipitated in the as-received hot forged commercially pure Ti. In addition, a large amount of the titanium hydrides can be introduced into Ti matrix with selective precipitation by using electrochemical treatment. Cs-corrected scanning transmission electron microscopy is used to study the precipitation mechanisms of the two hydrides. It is revealed that the gamma-hydride and delta-hydride precipitations are both formed through slip + shuffle mechanisms involving a unit of two layers of titanium atoms, but the difference is that the gamma-hydride is formed by prismatic slip corresponding to hydrogen occupying the octahedral sites of alpha-Ti, while the delta-hydride is formed by basal slip corresponding to hydrogen occupying the tetrahedral sites of alpha-Ti. (c) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

In this study, it was found that gamma-hydride and delta-hydride phases with different specific orientations were randomly precipitated in hot forged commercially pure Ti, and a large amount of titanium hydrides can be selectively introduced into the Ti matrix through electrochemical treatment. Cs-corrected scanning transmission electron microscopy was used to study the precipitation mechanisms of these two hydrides, revealing they are formed through different slip mechanisms involving two layers of titanium atoms.