HYDROGEN EFFECTS ON THE INTERACTION BETWEEN DISLOCATIONS

The effect of hydrogen on the interaction between dislocations and oth er elastic centers (impurity atoms and dislocations) in 310 S stainles s steel and high-purity aluminum has been directly observed during def ormation experiments in situ in an environmental cell transmission ele ctron microscope. In 310 S stainless steel, the presence of hydrogen w as observed to reduce the elastic interactions between obstacles and p erfect and partial dislocations; thus, enhancing the mobility of the d islocations. In high-purity aluminum, the introduction and removal of hydrogen from the system was observed to cause a reversal in the direc tion of motion of the dislocations piled up against a barrier; consist ent with a reduction of the elastic interactions by solute hydrogen. T hese observations provide direct support for the hydrogen shielding me chanism that has been proposed to account for the observed hydrogen-en hanced mobility of dislocations. (C) 1997 Acta Metallurgica Inc.