Finite-element analysis of radial extrusion for a thin disk with severe-plastic deformation

Abstract

Severe plastic deformation is an effective method to obtain fine or ultrafine grains in metallic materials. In the present study, a radial extrusion of a round bar was investigated for the capability of producing a thin disk by severe plastic deformation by the rigid-plastic finite-element method. Similar to the deformation mechanism in the ECAP, the shear deformation was observed to develop at the corner of the container; its magnitude increases as the radius of the corner decreases. Additional plastic deformation was obtained as the material flowed in the radial direction. However, waviness of the sheet in the radial direction and occurrence of cracking were observed at the periphery of the disk. To resolve these problems, the bottom surface of the container was conically designed in order to provide an inclination angle along the radial direction. This process was further modified to a radial extrusion of a pipe for a hollow disk or thin ring with severe-plastic deformation.