Mechanics of the hydrogendashdislocationdashimpurity interactions—I. Increasing shear modulus

Abstract

The effect of hydrogen on dislocationdashdislocation and dislocationdashimpurity atom interactions is studied under conditions where hydrogen is in equilibrium with local stresses and in systems where hydrogen increases the shear modulus. In the case of two edge dislocations (plane strain) the effect of hydrogen is modeled by a continuous distribution of dilatation lines whose strength depends on the local hydrogen concentration. The hydrogen distribution in the atmospheres is adjusted to minimize the energy of the system as the dislocations approach each other. The iterative finite element analysis used to calculate the hydrogen 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 dislocationdashinterstitial solute atom interaction and on the screw dislocationdashinterstitial solute atom interaction is discussed using a finite element analysis and the atom interaction energies are calculated in the presence of hydrogen. For the case where hydrogen increases the shear modulus, a significant hydrogendashrelated decrease of the edge dislocationdashinterstitial solute atom interaction energy was observed when the edge dislocationdashsolute distance is approximately less than two Burgers vectors. Depending on the orientation of the tetragonal axis of the interstitial solute distortion field, hydrogen may strengthen or weaken the interaction between the screw dislocationdashinterstitial solute.