Numerical Investigations on Material Flow During Indirect Extrusion of Copper-Clad Aluminum Rods

In the extrusion of clad composite materials with different flow stresses are usually used. This causes an inhomogeneous material flow which can induce sleeve or core fracture. In the present study, the material flow during indirect extrusion of copper-clad aluminum (CCA) rods was analyzed by means of experimental and numerical investigations throughout the process. In order to provide material models for the numerical analysis hot compression tests of the aluminum alloy EN AW-1080A and the copper alloy CW004A were carried out. The indirect extrusion was performed using a conical die with a semi die angle of 45° and an extrusion ratio of 14.8:1. The container was heated to 330°C, while billet, die, and ram were kept at room temperature. The extrusion trial was then modeled with the FEM based software DEFORM 2D. Cross sections were taken from the extruded rod and compared to the corresponding sections of the simulation with regard to the development of the equivalent copper cross section. As a result, the development of extrusion force and equivalent copper cross section could be clarified. The numerical investigations indicated a higher flow velocity for the aluminum core than for the copper sleeve at the bearing channel. Therefore, high tensile stresses and fractures of the copper sleeve were induced. Additionally, the validated numerical analysis made possible to determine the conditions for a successful co-extrusion of the analyzed CCA rod.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Numerical analysis of plastic die deformation during high temperature copper extrusion

In copper extrusion, billet temperatures of 600°C or more are very common and the dies are therefore exposed to high thermo-mechanical stress. This causes deflection and wear of the dies and thus reduced quality of the extruded profile. In the present study, die deflection and residual deformation after several extrusion cycles was investigated by means of extrusion trials and numerical analyses. Material models of four tool materials (hot-work tool steels 1.2367 and CS1, nickel-based alloy 718, cobalt-based alloy Stellite 1) and the copper alloy CW024A were provided by hot compression tests. Extrusion trials were carried out applying four different dies, each made of another tool material. Using the FEM based software DEFORM 2D, the extrusion trials were modeled and decoupled die stress analyses were performed, which simulated three consecutive load cycles. The focus of the data interpretation was in die deflection in proximity of the die land due to the thermo-mechanical load and residual plastic deformation after relief of the mechanical load. Larger values of deflection close to the die land were observed for the hot-work tool steels, while the deflection of nickel- and cobalt-based alloys was negligibly small. Also, remarkable plastic deformation was only determined for the hot-work tool steels, with increasing values for every simulated load cycle. This analysis characterizes the performance limits of hot-work tool steels and the benefits of nickel- and cobalt-based alloys regarding contour accuracy during high temperature copper extrusion