Hydrogen permeation in rapidly quenched amorphous and crystallized Nb_(20)Ti_(40)Ni_(40) alloy ribbons

摘要

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 Kφ_(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.