The effect of H upon the interaction between dislocations and other elastic centers, such as impurity atoms and dislocations, was directly observed in stainless steel and high-purity Al during  in situ  deformation in an environmental-cell transmission electron microscope. In the case of the steel, the presence of H was observed to reduce the elastic interaction between obstacles and perfect or partial dislocations, thus enhancing the mobility of the dislocations. In high-purity Al, the introduction and removal of H from the system was observed to cause a reversal in the direction of motion of dislocations which piled up against barriers. This was consistent with a reduction in elastic interactions, due to dissolved H. The observations provided direct support for the H-shielding mechanism that had been proposed in order to account for an observed H-enhanced mobility of dislocations.

Hydrogen Effects on the Interaction between Dislocations P.J.Ferreira, I.M.Robertson, H.K.Birnbaum: Acta Materialia, 1998, 46[5], 1749-57