Microstructural Changes and Hydrogen Permeability of Rolled and Annealed Nb30Ti35Co35 Alloys

Relationship between microstructural changes and hydrogen permeabilities of rolled and annealed Nb30Ti35Co35 alloys has been investigated. In the as-cast state, the alloy has a lamellar structure consisted of bcc-(Nb, Ti) and B2-TiCo phases. Hydrogen permeability was decreased with increasing rolling reduction. Granule (Nb, Ti) phase was formed in the TiCo matrix after annealing between 1173 K and 1373 K. Hydrogen permeability of non-rolled alloys was almost constant after microstructural change by annealing. On the contrary, hydrogen permeability of rolled alloys was increased with increasing annealing temperature, recovered to 90％ of the as-cast alloy by annealing at 1373 K, which is quite larger than the value expected by the mixing rule consisted of both two phases. Therefore, rolling and annealing technique is effective for industrial preparation of Nb-TiCo alloy foil to obtain large hydrogen flux for hydrogen production.