Influence of Shear Moduli and Lattice Parameters on the Equilibrium of a Screw Dislocation*

Using the Peierls model of a dislocation, the simultaneous effects of shear moduli and lattice parameters on the equilibrium of a screw dislocation in a material composed of soft and hard phases are examined. The dependence of the mobility of dislocations on the hardness of alloys due to these two forms of inhomogeneities is obtained. The existing literature on the subject of a screw dislocation in a bimetallic medium does not consider the effect of differences in lattice parameters and gives the result that a material with higher shear modulus will always repel a dislocation located in a material of lower shear modulus. In contrast to this, it is found that a material with higher shear modulus will either attract or repel a screw dislocation depending on the com-bination of elastic constants and lattice parameters for the medium. The use of continuous distribution of dislocations removes the diffi-culties encountered by a singular model when the dislocation approaches the interface. 1