Nondestructive Observation of Dislocation Structures Formed at Fatigued Copper and Stainless Steel Crystals

Abstract

Dislocation structures of fatigued metallic materials were investigated using electron channelling contrast imaging (ECCI) technique using a scanning electron microscope. By imaging electron channelling contrast resulting from dislocations, we could observe the dislocations lying close to crystal surface. At a fatigued copper single crystal of single slip orientation, the ECCI technique successfully imaged ladder-like dislocation structure peculiar to persistent slip band (PSB). In fatigue tests on copper bicrystals, effect of grain boundary on the PSB distribution was confirmed by the ECCI observation. This ECCI technique was attempted also to reveal the change in the dislocation structure of a stainless steel during fatigue.