Dislocation structures in nickel during high temperature low cycle fatigue at large cumulative strains

Abstract

The development of the dislocation arrangement during high temperature low cycle fatigue in nickel polycrystals was investigated. Special attention was paid to dislocation structures in the vicinity of grain boundaries. It was found that a defined cell structure develops during progressing cyclic deformation. The motion of grain boundaries associated with high temperature cyclic deformation leads to a dislocation structure gradient in the wake of the boundaries. These structure gradients are suspected to be prone to setting off nucleation of dynamic recrystallization. Upon strain path changes the fatigued structure was observed to become gradually superimposed by a new cell structure without prior decomposition.