The relationship between the microstructural changes and hydrogen permeability of rolled and annealed Nb₃₀Ti₃₅Co₃₅ alloys was investigated. The as-cast alloy had a lamellar structure that consisted of bcc-(Nb, Ti) and B2-TiCo phases. Hydrogen permeability decreased with increasing rolling reduction. The granule (Nb, Ti) phase formed in the TiCo matrix after annealing at temperatures of 1173 to 1373 K. The hydrogen permeability of the non-rolled alloys after annealing, which caused microstructural changes, was almost independent of annealing temperature. In contrast, the hydrogen permeability of the rolled alloys increased with increasing annealing temperature. It recovered to 90% of that for the as-cast alloy after annealing at 1373 K, which is higher than the value predicted by the mixing rule for the two phases. Therefore, rolling and annealing effectively increase the hydrogen flux for the industrial preparation of Nb–TiCo alloy foil for hydrogen production.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 85 (2021) 338–344. The captions of Fig. 1, 2, 3, 5, 6 are slightly modified.