Microstructure dependent hydrogen permeability in eutectic Nb30Ti35Co35

• Various eutectic structures of Nb30Ti35Co35 alloy are produced.
• Aligned directionally solidified structure shows the highest hydrogen permeability.
• Rolled structure shows the lowest hydrogen permeability.
• Mixing rule is effective to predict hydrogen permeability of eutectic Nb30Ti35Co35.

Nb30Ti35Co35 eutectic composites with various structure patterns were produced by directional solidification (DS), rolling and annealing. The relationship between structure and hydrogen permeability is investigated and discussed on the basis of the mixing rule. The measured hydrogen permeability of the parallel-type structure with the two eutectic phases aligned in parallel to the hydrogen permeation direction (generated by DS) is significantly higher than those measured for the other structure types. In contrast, a series-type structure with the two phases aligned perpendicular to the hydrogen permeation direction (generated by rolling) induces the lowest permeability. The variation of hydrogen permeability with different structure patterns is quantitatively explained by the mixing rule.