Diffusion of Hydrogen in the Ni₃₀Ti₅₀Cu₂₀ Shape Memory Alloy

The chemical diffusion coefficient (Dc) of hydrogen in the Ni30Ti50Cu20 shape memory alloy has been determined in the temperature range 700 - 1150 K by investigating the kinetics of H2 absorption. The mobility of H has also been deduced between 250 K and 280 K from a Snoek-type internal friction peak. The values of the Einstein diffusion coefficient (DE) derived from the relaxation time of this peak were in keeping with those of Dc obtained at low H contents (nH = H/Me < 0.01 ). The combined Arrhenius plot of DE and Dc gave the following values for the diffusion parameters: W = 0.52 ± 0.02 eV, D0 = (5±2)x10-4 cm2/s.