The widths of glissile extended dislocations in anisotropic face-centred cubic crystals

Abstract

A total dislocation in a face-centred cubic crystal can dissociate to form a glissile extended dislocation on a {111} plane. The latter consists of two Shockley partial dislocations connected by a stacking fault. An analysis of dislocations based on anisotropic elasticity theory has been employed to calculate the force between the Shockley partials as a function of orientation in eight f.c.c. elements. In all cases the force was found to be repulsive, i.e. the dissociation is always energetically favourable in these elements. It is also shown, however, that there are permissible elastic constant values in the anisotropic case for which the dissociation is not energetically favourable. The widths of the glissile extended dislocations in the various f.c.c. elements have been computed as a function of stacking-fault energy. The anisotropic results have been compared with those derived from two isotropic approximations: the first employing average values of the elastic constants, the second employing values appropriate for a {111} plane. The latter was found to be an excellent approximation to the anisotropic results.