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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 copperclad 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.

The backward rod extrusion of bimetallic aluminum-copper alloys at room temperature was investigated. The aluminum alloy EN AW-1080A and the copper alloy Cu-ETP were selected to prepare the core and sleeve of the billet respectively. The copper cross section was equivalent to 30% of the billet. Moreover, the billet was extruded applying a conic die angle of 90° and an extrusion ratio of 14:1. Experimental results demonstrated that the combination of grounding marks on the die surface and the application of graphite foil reduced drastically the friction between copper and the conic die. Thus, a uniform material flow of aluminum and copper through the bearing channel was observed during the steady state of the extrusion process. However multiple fractures of the copper sleeve occurred at the end of the process. The extrusion process was numerically simulated applying the FEM-based software Deform 2D in order to estimate the state variables and material flow. The die and punch temperature evolution, as well as the die extrusion force were recorded during the whole process to facilitate the validation of the numerical analysis.

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The Young's modulus for a series of binary Mg–Gd and Mg–Nd alloys are studied in the present work. Fine and homogeneous grain structures are prepared by using hot extrusion. The results demonstrate that the Young's modulus of Mg–Gd alloys increase linearly by the increase of Gd in solid solution. Aging treatments are applied to the Mg–0.79–2.43 at% Gd alloys. A needle‐like orthorhombic structure β′ phase is formed in Mg matrix. Due to a higher Young's modulus of the intermetallic β′ phase which is estimated to be 80 GPa, the Young's modulus of Mg–Gd alloys are enhanced by aging. The results for Mg–Nd alloys indicate that Young's modulus firstly decreases and reaches 42.53 GPa for Mg–0.18 at% Nd which is attributed to the solid solution of Nd in Mg. The Mg41Nd5 particles appear in Mg matrix when Nd content is higher than 0.18 at%, and Young's modulus of the particles is tested as 57.0 GPa. Thus, the Young's modulus increases to 43.42 GPa for Mg–0.63 at% Nd. The Young's modulus of Mg alloys are affected by altering the crystal cell parameters with solid solutes, and/or the formation of precipitate phases with varying amounts.