Nucleation of slip bands near twin boundary in high-cycle fatigue

Abstract

In order to investigate the criterion for the persistent slip band (PSB) formation near a Σ3(111) coherent twin boundary, where is a preferential site for formation of PSB, a high-cycle fatigue test is carried out at room temperature using a copper bicrystal specimen with the twin boundary. PSBs are observed near the boundary in the connection with the evolution of extrusion/intrusion on the specimen surface. The slip behavior is different from that predicted by the Schmid factor. A finite element method (FEM) analysis is conducted for the bicrystal, and it reveals that the increase of resolved shear stress on the specific slip system due to the constraint of deformation between the crystals is the main cause for promoting the nucleation of PSB near the twin boundary. By taking into account the interaction between the primary and the secondary slip systems, it is possible to specify the formation behavior of PSB near the twin boundary.