AN ELASTICITY CALCULATION OF INTERACTION BETWEEN A MISFIT DEFECT AND AN EXTENDED DISLOCATION IN FCC METALS

A rigid dislocation model was used to calculate the effect of the extension of a dislocation on the yield stress in a f.c.c. metal. In this calculation a generalization was made to include all dislocation characters from pure edge to pure screw orientations. Three types of point defects were considered as obstacles to dislocation motion: two produce a 〈100〉 distortion and the third a spherical distortion of the lattice. The resistance to dislocation motion due to these obstacles was generally reduced as the width of the extended dislocation increased. The magnitude of the resistance for a widely extended dislocation was about 60% of that for a perfect (unextended) dislocation, which was expected considering the magnitude of Burgers vectors of the two cases. The effect of the extension on the resistance to dislocation motion saturated at a relatively small dislocation width (a few atomic distances). This means that, even in a metal like aluminum which possesses a high stacking fault energy, a dislocation cannot be treated as a perfect dislocation when the obstacles are atomistic point defects. For such a slightly extended dislocation, the maximum resistance due to a 〈100〉 defect was found near the screw orientation rather than the edge orientation. The resistance to dislocation motion due to a defect with spherical symmetry was as large as that due to a defect with 〈100〉 tetragonality. © 1969.