The kinetics of dislocation climb over hard particles—I. Climb without attractive particle-dislocation interaction

Abstract

The effect of hard particles of low volume fraction on the creep strength is studied theoretically in a two-part paper. Here in part I, the kinetics of dislocation climb over a particle is modelled assuming that the particle does not exert an attractive force on the dislocation (“non-interacting” particle). The shape of the climbing dislocation is given by a minimum energy condition, which is shown to rule out purely “local” climb (as considered in previous models). A natural power-law dependence of the dislocation velocity on the applied stress, with n ranging from about 3 to 4, is obtained, and only a small threshold stress can be identified. The results appear compatible with the creep behaviour of alloys strengthened by coherent precipitates, but are totally at variance with experimental threshold stress data for materials with incoherent particle dispersions.