Comparison of fatigue lives between grain boundaries and component single crystals of copper bicrystals

Abstract

Abstract Fatigue lives of grain boundaries (GBs) and component crystals were measured by using [123]/[335] and [5 9 13]/ [579] Cu bicrystals with a perpendicular GB at room temperature in air. The results show that the GBs were always the preferential sites for fatigue crack initiation and propagation in the two groups of bicrystals under cyclic tensiontension loading as well as push-pull straining control. When an [123]/[335] bicrystal with reduced section area was tested by cyclic tension-tension loading, the [335] component crystal always had a relatively higher fatigue life than the [123] component crystal. As a result, the fatigue life increased in the order of GB, [123] and [335] component crystals. When the two groups of bicrystals were subjected to cyclic push-pull straining, the GB of the [5 9 13]/[579] bicrystal showed a higher fatigue life than that of the [123]/[335] bicrystal, which was suggested to be partially attributed to the difference in the component crystal orientations in the two bicrystals. By using scanning electron microscopy and electron channeling contrast techniques, the fatigue damage features on the surfaces and fatigue fractography were examined. Based on the present results, the fatigue cracking mechanisms along GBs and persistent slip bands in Cu bicrystals are discussed.