In order to detect persistent slip bands which could be the nuclei of fatigue cracks, the surfaces of fatigued Cu single crystals were observed by using electron channeling contrast imaging methods. This permitted the non-destructive observation of dislocation structures which existed near to the surface of bulk crystals. Single crystals having [231], [001] or [111] tensile axes were cyclically deformed at a constant plastic shear strain amplitude of 2 x 10−3. Following fatigue tests, electron channeling contrast imaging observations were made of the crystal surfaces by using a field-emission scanning electron microscope. When the [231] single crystals were fatigued up to 1500 cycles, band-like images along a primary slip plane were detected by using the electron channeling contrast imaging method. It was found, using high-magnification observations, that the band-like image comprised a ladder-like structure. Because this structure was identical to the persistent slip bands which were observed using transmission electron microscopy, it was concluded that the band-like images in electron channeling contrast imaging were the persistent slip bands which formed near to crystal surfaces. Electron channeling contrast images of fatigued single crystals with [001] or [111] axes revealed linear and wavy structures, respectively, which lay perpendicular to the tensile axis. These structures were also analogous to those seen when using transmission electron microscopy.

Observation of Dislocation Structure of Fatigued Copper Single Crystals using ECCI Method. Y.Kaneko, S.Hashimoto: Journal of the Japan Institute of Metals, 2002, 66[12], 1297-303