Microstructures near fracture surfaces of copper specimens were investigated using the electron channelling contrast imaging method. The purpose of the present study was to find a new criterion for analyzing fracture process instead of a conventional fractographic technique. In the present study, the electron channelling contrast imaging observations were conducted on strip and center-cracked tensile specimens of a polycrystalline copper, which were fractured under monotonic tensile straining or fatigue loading. The electron channelling contrast imaging observation revealed that the cell, the vein, and the ladder-like dislocation structures were formed near the fracture surface of the strip specimen fractured under fatigue, although no vein and ladder-like structures were found in the monotonically strained specimen. It was suggested that the distinction between the fatigue fracture and the monotonic tensile fracture could be achieved from the electron channelling contrast imaging observation near the fracture surfaces. Also measured were the sizes of the region which contained the cell structures at the fatigue crack propagating in the center-cracked tensile specimen. It was confirmed that the size of the cell-structured region increased with increasing stress intensity factor range ΔKI. By measuring the sizes of the cell-structured regions of the strip specimen, the distribution of the ΔKI value along the fracture surface could be obtained from the preliminarily-measured relationship between the cell-structured region size and the ΔKI value. This kind of the ΔKI distribution will give important information such as crack nucleation site and crack growth direction, which was required for a better understanding of fatigue fracture process.

A Dislocation-Based Approach to Identify Fracture Process. Y.Kaneko, Y.Honda, S.Hashimoto: IOP Conference Series - Materials Science and Engineering, 2009, 3[1], 012019