Mechanism of climb of dissociated dislocations

The 'weak-beam' electron microscopy technique has been used to study the climb of dissociated dislocations in a Cu-13.43% Al alloy under conditions of high supersaturation of point defects introduced by electron irradiation at room and elevated temperatures. Prismatic loops (assumed to be of the interstitial type because of the dislocation 'bias') are found to be nucleated on the individual partials. The Burgers vectors of the nucleated loops are a function of the dislocation character, and are such as to minimize the elastic energy of the resultant configuration (partial plus loop), and to maximize the edge component of the loops. For orientations other than pure edge, climb involves the generation of Burgers vectors different from those of the original partials. The complex dislocation configurations formed by climb at elevated temperatures can be understood in terms of the nucleation of prismatic loops and their growth in directions controlled by the climb force on the parts of the prismatic loops not lying in the glide plane of the dislocations. (author)