THE MECHANICS AND ENERGETICS OF CROSS-SLIP

Dislocation cross-slip plays an important part in many deformation processes, such as recovery, recrystallisation, creep and fatigue, but has never been treated theoretically except by approximate methods and within the line tension model. An accurate, numerical treatment of cross-slip, using the full self-stress dislocation model applied to face-centred cubic materials within a mesoscale, linear elastic framework is presented. Results are compared with experiment and with existing analytic approximations. The Friedel-Escaig model of cross-slip is found to be preferred over that due to Schoek and Seeger. It is shown further that the line tension model of cross-slip is inadequate, due to neglect of self-stress dipole forces. Good agreement is found with experimentally determined values of the critical stress and activation volume for cross-slip. It is argued that significant discrepancies between the theoretical and experimental orientation dependence of the cross-slip stress cast doubt on prevailing mechanistic theories.