Effect of elements addition on hydrogen permeability and ductility of Nb40Ti18Zr12Ni30 alloy

Nb40Ti18Zr12Ni25M5 (M = Al, Co, Cu or Pd) alloys were prepared by arc melting in a purified argon atmosphere. Microstructures, ductility, hydrogen permeability (Φ) and activation energy Ea for hydrogen permeation of these alloys have been investigated by scanning electron microscopy (SEM), cold-rolling and a gas permeation technique, respectively. Although both Nb40Ti18Zr12Ni25Al5 and Nb40Ti18Zr12Ni25Pd5 alloys were brittle in the as-cast state, they were hydrogen permeable. Both Nb40Ti18Zr12Ni25Cu5 and Nb40Ti18Zr12Ni25Co5 alloys showed good ductility, which was meaningful to decrease the thickness by cold-rolling. The values of Φ673 K for the Nb40Ti18Zr12Ni25Al5 and the Nb40Ti18Zr12Ni25Co5 alloys at 673 K were 3.73 × 10−8 and 3.82 × 10−8 [mol H2 m−1 s−1 Pa−1/2], which were higher than that of the base one (Nb40Ti18Zr12Ni30 alloy). On the other hand, Cu and Pd showed little effect on hydrogen permeability. The Nb40Ti18Zr12Ni25Co5 alloy showed the highest hydrogen permeability, ductility and resistance to the hydrogen embrittlement among the alloys investigated in the present work. This alloy is a promising hydrogen permeable membrane.