Thermal hydrogen desorption behavior of cathodically charged Ni3(Si,Ti) alloys

Using thermal hydrogen desorption spectroscopy, the effects of lattice defects and boron-doping on the hydrogen desorption behavior in the cathodically charged L12-type Ni3(Si,Ti) compounds were investigated. Low- and high-temperature peaks were observed, and attributed to interstitial sites in L12 lattice and grain boundaries, respectively, as the trap sites of hydrogen. The low-temperature peak increased by deformation while the high-temperature peak was insensitive to deformation. The boron-doping to the Ni3(Si,Ti) specimen has the effect of reducing the desorped hydrogen contents in the measured whole temperatures. As the holding time after hydrogen charging proceeds, the low-temperature peak rapidly decreased while the high-temperature peak remained constant. It is suggested that during holding time, hydrogen atoms in the interstitial sites in the L12 lattice migrate to the outside of the material while those at the grain boundaries remain at the same level. The hydrogen atoms in the interstitial sites in the L12 lattice in the deformed specimen can migrate through dislocations or with the help of excess vacancies more quickly than those in the recrystallized specimen. The results obtained in this study are discussed in relation to the environmental embrittlement of Ni3(Si,Ti) compounds