The kinetics of dislocation climb over hard particles. - 2 : Effects of an attractive particle dislocation interaction

Abstract

A model for the high-temperature creep strength of dispersion strengthened materials is presented. It is based on part I of this paper which treated dislocation climb over "non-interacting" particles. The present part II deals with the kinetics of dislocation climb over hard particles which exert an attractive force on the dislocations. The attraction is shown to affect the climb and bypass process in two ways : (i) above a certain stress, local climb becomes a stable mechanism, and (ii) a strong threshold stress appears for detachment of the dislocation from the particle. Thermal activation of the detachment process and aparticle dragging are incorporated and shown to affect the threshold stress for very small particles. Qualitative comparison of predictions with the creep behaviour of dispersion-strengthened materials suggests that an attractive interaction is probably the key to a better understanding of the highly stress-sensitive creep rate in these materials.