Design of (Nb, Mo)(40)Ti(30)Ni(30) alloy membranes for combined enhancement of hydrogen permeability and embrittlement resistance

The effect of substitution of Nb by Mo in Nb(40)Ti(30)Ni(30) was investigated with respect to microstructural features and hydrogen dissolution, diffusion and permeation. As-cast Nb(40−x)Mo(x)Ti(30)Ni(30) (x = 0, 5, 10) alloys consist of primary bcc-Nb phase and binary eutectic (bcc-Nb + B2-TiNi). The substitution of Nb by Mo reduces the hydrogen solubility in alloys, but may increase (x = 5) or decrease (x = 10) the apparent hydrogen diffusivity and permeability. As-cast Nb(35)Mo(5)Ti(30)Ni(30) exhibits a combined enhancement of hydrogen permeability and embrittlement resistance as compared to Nb(40)Ti(30)Ni(30). This work confirms that Mo is a desirable alloying element in Nb that can contribute to a reduction in hydrogen absorption and an increase in intrinsic hydrogen diffusion, thus improving embrittlement resistance with minimal permeability penalty.