MECHANICS OF THE HYDROGEN-DISLOCATION-IMPURITY INTERACTIONS .1. INCREASING SHEAR MODULUS

The effect of hydrogen on dislocation-dislocation and dislocation-impu rity atom interactions is studied under conditions where hydrogen is i n equilibrium with local stresses and in systems where hydrogen increa ses the shear modulus. In the case of two edge dislocations (plane str ain) the effect of hydrogen is modeled by a continuous distribution of dilatation lines whose strength depends on the local hydrogen concent ration. The hydrogen distribution in the atmospheres is adjusted to mi nimize the energy of the system as the dislocations approach each othe r. The iterative finite element analysis used to calculate the hydroge n distribution accounts for the stress relaxation associated with the hydrogen induced volume and the elastic moduli changes due to hydrogen . The interactions between the dislocations are calculated accounting for all the stress fields due to dislocations and hydrogen atmospheres . Modeling of the hydrogen effects on the edge dislocation-interstitia l solute atom interaction and on the screw dislocation-interstitial so lute atom interaction is discussed using a finite element analysis and th atom interaction energies are calculated in the presence of hydrog en. For the case where hydrogen increases the shear modulus, a signifi cant hydrogen-related decrease of the edge dislocation-interstitial so lute atom interaction energy was observed when the edge dislocation-so lute distance is approximately less than two Burgers vectors. Dependin g on the orientation of the tetragonal axis of the interstitial solute distortion field, hydrogen may strengthen or weaken the interaction b etween the screw dislocation-interstitial solute.