OS0729 Growth behaviour of a small crack in ultrafine grained copper processed by ECAP

Abstract

High-cycle fatigue tests were carried out on smooth specimens of ultrafine-grained copper produced by equal channel angular pressing(ECAP). Grain sizes of 300nm were formed after twelve passages of ECAP pressing by Be route. Fatigue tests were conducted using a rotating bending fatigue machine. A major crack, which led to the final fracture of the specimen, initiated from shear bands. After initiation, Hie growth rate increased with an increase in crack length. However, a decrease in growth rate with a change in growth path morphology occurred when the crack length 0.10.3mm, respectively. This decrease occurred because of a change in the crack growth mechanism and is explained by considering the interrelation between grain size and the reversible plastic zone size at the crack tip.