ECCI法による銅単結晶の疲労転位構造の観察

Abstract

In order to detect persistent slip bands (PSBs) which can be nucleus of fatigue cracks, surfaces of fatigued copper single crystals were observed using electron channeling contrast imaging (ECCI) method. The ECCI method enables us to observe dislocation structure existing near the surface of bulk crystal, nondestructively. The copper single crystals having [2\bar31], [001] and [\bar111] tensile axes were cyclically deformed at a constant plastic shear strain amplitude of 2×10−3. After the fatigue tests, the ECCI observations of the crystal surfaces were performed with a field-emission scanning electron microscope. When the [2\bar31] single crystals were fatigued until 1500 cycles, band-like images along a primary slip plane were detected by the ECCI method. It was found at high-magnification observation that the band-like image was composed from ladder-like structure. Because this structure is identical to the PSB which has been observed with transmission electron microscope (TEM), it can be concluded that the band-like images of the ECCI observation were the PSBs which were formed near crystal surface. The ECC images of the fatigued single crystals having [001] and [\bar111] axes revealed linear and wavy structures lying perpendicular to tensile axis, respectively. These structures were also analogues to the observations which have been conducted using the TEM.