The effect of lattice defects on hydrogen thermal desorption of cathodically charged Co3Ti

Using the thermal hydrogen desorption spectroscopy (THDS), the effects of lattice defects such as vacancies, dislocations and grain boundaries on the desorption behavior of hydrogen in the cathodically charged Co3Ti were investigated. The low-temperature and high-temperature peaks were observed in the hydrogen thermal desorption curves, and as the trap sites of hydrogen, interstitial sites in L12 lattice and grain boundaries were suggested. The low-temperature peak was enhanced by deformation while the high-temperature peak was affected by grain size. As the holding time after hydrogen charging proceeded, the low-temperature peak decreased while the high-temperature peak increased. This change was faster and more significant in the deformed specimen than in the recrystallized specimen. It was suggested that during holding time hydrogen atoms migrate from the interstitial sites in L12 lattice to grain boundaries that are energetically deeper trap sites. The hydrogen atoms 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 were discussed in the association with the environmental embrittlement of L12 intermetallic compounds.