Solute-dislocation interactions: modelling and experiments in hydrogenated nickel and nickel base alloys

The dynamic interaction between diffusing hydrogen and mobile dislocations in nickel and binary nickel–16 wt.% chromium is analysed in terms of the solute drag phenomenon. Static strain ageing experiments are used to measure the saturated dislocation pinning force as a function of the hydrogen concentration. Hydrogen-dislocation interactions cause a shielding of the pair interactions between edge dislocations. The influence of this screening effect is analytically evaluated on the line tension of curved dislocations, and we assess its consequences on the critical force for the expansion of a dislocation loop and on the dissociation mechanism. These results are used to interpret experimental results on the plastic flow of hydrogen-charged nickel single crystals oriented for easy glide. This study illustrates the mechanisms of H-dislocation interactions and their consequences on the different contributions of hydrogen to the flow stress of nickel.