Abstract
Reported thermal desorption curves were subjected to peak separation by Gaussian distribution to evaluate numerically the state of hydrogen. The curves had been obtained on heavily cold rolled pure iron that was hydrogen-charged by cathodic polarization at different temperatures and current densities. All the curves were successfully decomposed into sub-peaks corresponding to lattice, dislocation, grain boundary, vacancy and vacancy cluster. The hydrogen partitioning among them were sophisticatedly depending on the charging temperature. Hydrogen in lattice or trapped by dislocation ever decreased with temperature until 363K;hydrogen trapped by vacancy type defects (vacancy or vacancy cluster) increased up to 363K. The amount of hydrogen trapped by grain boundary had a combined feature of these two types, presenting its maximum at 333K. As trap efficiency of all traps decreased monotonously with charging temperature, temperature dependence of trap densities is important. Density of dislocation trap was almost unaffected, that of grain boundary trap increases up to around 333K, and those of vacancy and vacancy cluster 363K. These features are useful for deciding hydrogen charging temperatures that is corporative to fracture mode;quasi-cleavage or inter-granular fracture which is relevant to vacancy type traps or grain boundary trap respectively. They are also useful in judging the temperature of hydrogen entry, through the straightforward relation between the amounts of hydrogen trapped by dislocation and grain boundary.
