On the symmetrical role of cross-slip of screw dislocations and climb of edge dislocations as recovery processes controlling high-temperature creep

Abstract

A general model for high-temperature recovery-controlled creep is proposed. Cross slip of screw dislocations is introduced on an equal footing with climb of edge dislocations as a recovery process : cross slip and climb operate as two parallel concurrent mechanisms controlling the creep rate. A constitutive equation is derived from simple assumptions : Climb and cross slip are dominant in different domains of T and σ according to the relative magnitudes of the activation energies for self-diffusion QSD and cross slip Q CS(σ). The stress dependence of ἐ does not follow a power law except when climb is dominant, and intermediate values of apparent stress exponents are attributed to the existence of a transition domain. The published experimental evidence is compatible with this model ; the case of copper is reviewed as an example and it is shown that the low activation energy domain can be controlled by cross slip. The present approach is relevant to such problems as the influence of the stacking-fault energy on the creep rate or the creep of solid-solution alloys