Production, Annihilation and Migration of Point Defects in Cyclic Straining

Abstract

Interactions of mobile dislocations in persistent slip bands with ladder-like structure are analyzed and production rates of point defects, preferably vacancies, are derived. Previous resistivity measurements in copper single crystals and polycrystals are used to derive the growth of vacancy concentration during cyclic loading at low temperatures. The parameters of the growth law are derived from the initial growth rate and saturated vacancy concentration. The consequences of vacancy production in localized cyclic straining on the surface relief formation are analyzed. At very low temperature vacancies are produced and annihilated only athermally and vacancy concentration saturates. Localized deformation in persistent slip bands produces high vacancy concentration which outcomes in formation of tiny extrusions. At ambient and slightly elevated temperatures vacancies are steadily produced and migrate from the persistent slip bands to the matrix. This results in formation of persistent slip markings consisting of extrusions and intrusions. The shape of extrusions and intrusions depends on the on the dislocation arrangement in the PSB and in the neighbor matrix and their history during cyclic straining. Fatigue cracks start from sharp-edged intrusions.