The diffusivity of hydrogen in two Ni3Al alloys was measured at 100 to 420C using an ultrahigh-vacuum gaseous permeation technique. The diffusivity data fell into two segments, in which the hydrogen diffusivity obeyed the Arrhenius relationship. It was suggested that hydrogen transportation took place along the grain boundaries at lower temperatures, and in the lattice at higher temperature. The intergranular fracture of L12-type intermetallics induced by hydrogen at relatively low temperature resulted from hydrogen transportation along the grain boundaries, not through the lattice.

Diffusion of Hydrogen along the Grain Boundaries in Ni3Al Alloys. Cheng, X.Y., Wan, X.J., Wu, Q.Y., Sun, X.K.: International Journal of Materials and Product Technology, 2001, 2, 841-6

Figure 11

Diffusion of Ga, Ge, Nb and Ti in Ni3Al

Table 15

Arrhenius parameters for Ni3Al