Hydrogen permeation in rapidly quenched amorphous and crystallized Nb20Ti40Ni40 alloy ribbons

Abstract Formation of an amorphous ( a -) Nb 20 Ti 40 Ni 40 alloy by rapid quenching and its crystallization behavior were investigated by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. The B2-TiNi phase was firstly crystallized and the remaining amorphous ( a -) phase subsequently decomposed into the bcc-(Nb, Ti) + B2–TiNi phases. The crystallized ( c -) Nb 20 Ti 40 Ni 40 samples obtained by annealing above 1173 K were ductile and insusceptible to hydrogen embrittlement between 598 and 673 K. Hydrogen permeability at 673 K ( Φ 673 K ) for the a- and c -Nb 20 Ti 40 Ni 40 alloys were 8.1 × 10 −9 and (3.0–4.8) × 10 −9  mol H 2 /m/s/Pa 0.5 , respectively. Φ 673 K increased with the increase in the diameter of the bcc-(Nb, Ti) phase, although this led to poor resistance to hydrogen embrittlement. The lower hydrogen permeability of the c- Nb 20 Ti 40 Ni 40 alloy was due to its lower hydrogen diffusivity. The present work demonstrated that rapid quenching and subsequent annealing are useful to prepare thermally stable Nb–TiNi hydrogen permeation alloy membranes.