Finite element analysis of equal channel angular pressing of strain rate sensitive metals

In recent years, equal channel angular pressing (ECAP) has been the subject of intensive study in recent years due to its capability of producing fully dense samples having a ultrafine grain size. In this process, knowledge of the internal stress, strain and strain rate distribution is fundamental to the determination of the optimum process conditions for a given material. The properties of the ECAPed materials are strongly dependent on the shear plastic deformation behavior during ECAP, which is controlled mainly by die geometry, material properties, and process conditions. In this study, we applied the finite element method to obtain a better understanding the plastic deformation behavior of the workpiece during ECAP in terms of material flow properties and die geometries. The material flow stress, i.e. hardening behavior, was considered to be both strain rate dependent and strain dependent. The deformation within the workpiece is inhomogeneous unlike the ideal pure shear deformation. The mesh size dependence on the local deformation behavior in the deforming zone was addressed. The corner gap formation between the die and workpiece during the plane strain ECAP process was investigated. The mechanism of the corner gap formation is described in conjunction with the hardening behavior and local flow velocity of the workpiece in the deforming zone.