Dislocation structures in cyclically strained X10CrAl24 ferritic steel

Abstract

Dislocation structures in polycrystalline X10CrAl24 ferritic stainless steel cyclically strained with constant plastic strain amplitude to failure at room temperature were studied using transmission electron microscopy. The spatial arrangement of dislocations in the individual grains was determined using the oriented foil technique. The characteristic types of dislocation structures for plastic strain amplitudes from 10 −5 to 10 −2 were determined. The typical dislocation structures consisted of a random arrangement of mostly screw dislocations for the lowest plastic strain amplitudes ( ε ap < 5 × 10 −5), veins and walls intersected by ladder-like structure for medium plastic strain amplitudes (5 × 10 −5 < ε ap < 2 × 10 −3) and predominantly wall, labyrinth and cellular structures for the highest plastic strain amplitudes ( ε ap > 2 × 10 −3). Their relative fractions dependent on the applied plastic strain amplitude were quantitatively evaluated. Special attention was paid to cyclic softening which is discussed in terms of specific properties of dislocations in a body-centered cubic structure and the localization of cyclic plastic strain to persistent slip bands.