Diffusion of hydrogen in the shape memory alloy Ni47Ti40Hf10Cu3

The H chemical diffusion coefficient Dc has been determined in the Ni47Ti40Hf10Cu3 alloy from the kinetics of the gas/solid-surface reaction in the temperature range 350-1000 K. The mobility of H was also investigated by mechanical spectroscopy at temperatures included between 240 and 260 K, where a Snoek internal friction peak occurs for frequencies in the kHz range. The results on the Einstein diffusion coefficient DE obtained from the relaxation time of the Snoek effect were correlated to the high temperature absorption results. Combined Arrhenius plots of DE and Dc data allow to determine the H diffusion parameters to: W=0.47±0.01  eV, D0=2×10−3.0±0.2  cm2/s.