Formation of BCC TiFe hydride under high hydrogen pressure

Highlight
• TiFe alloy was hydrogenated under high hydrogen pressure of 5 GPa.
• BCC TiFe hydride was formed by the hydrogenation.
• The volume expansion of the BCC hydride was larger than that of a γ-hydride TiFeH1.9.
• Formation process was discussed from the structural viewpoint.

We investigated the hydrogenation of a binary TiFe alloy at 5 GPa and 600 °C by in situ synchrotron radiation X-ray diffraction measurements. After formation of a solid solution of hydrogen in TiFe, an order–disorder phase transition in the metal lattice of TiFe occurred, which yielded a BCC TiFe hydride. The unit cell volume of the BCC hydride increased by 21.0% after the hydrogenation reaction. The volume expansion was larger than that of a γ-hydride TiFeH1.9 prepared by hydrogenation near ambient conditions.