Dislocation cell walls with high dislocation density as effective hydrogen traps in Armco iron

Abstract The effect of cold rolling (CR) deformation on the hydrogen permeation and trapping behavior of pure iron was systematically investigated. Increased deformation resulted in a decreased effective hydrogen diffusion coefficient, an extended effective lattice interstitial hydrogen diffusion path length, and increased hydrogen trap densities. However, the proportion of irreversible hydrogen traps to all traps was constant irrespective of the deformation level in the range of 30%–70% CR and increased when the deformation reached 80%. This is because the dislocation cell wall is composed of a central layer with high trap‐binding capacity and an outer layer with low trap‐binding capacity. More importantly, once the dislocation density in the center layer of the dislocation cell walls reached a relatively high value due to the severe plastic deformation, these regions become effective irreversible hydrogen traps.