OS1525 Fatigue Crack Growth of Ultrafine Grained Copper Processed by Different ECAP Pass-numbers

Abstract

Rotating bending fatigue tests on plain specimens were carried out for ultrafine grained copper. The specimens were produced by equal channel angular pressing with 4 passes (UFG4) and 12 passes (UFG12). The growth behavior of a small surface-crack was monitored. A major crack, which led to the final fracture of the specimen, initiated from slip bands and shear bands. After initiation, the crack grew linearly in the shear direction of the final pressing. There were different morphological features in fracture surfaces between UFG4 and UFG12. This difference could be explained by a quantitative model with the reversible plastic zone size and grain size.