The interaction of dislocations and inclusions during creep

Abstract

The relative importance of dislocation climb and inclusion drag is assessed for the creep of materials containing arrays of inclusions. It is shown that at high temperatures, dislocations can escape from elastically-hard particles by climb before significant dragging occurs. At lower temperatures or for fine particles, interfacial diffusion around particles may increase the particle mobility relative to climb and drag can occur. Under these conditions particle collection leads to a steady particle spacing on the dislocation where the rate of escape by climb balances the rate of capture. Once again the overall velocity is climb-controlled.

For elastically-soft inclusions, the applied stress must overcome the attractive interaction energy between dislocations and inclusions in order to escape. In the limiting case of cavities, the escape stress is approximately equal to the looping stress. Thus at stresses less than μb/Λ cavities remain attached to dislocations.