Progress in Extrusion Technology and Simulation of Light Metal Alloys

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Authors: Alessandro Selvaggio, Antonio Segatori, Ahmet Güzel, Lorenzo Donati, Luca Tomesani, A. Erman Tekkaya
Abstract: In the paper experimental investigations aimed at allowing a detailed and accurate comparison of different FEM codes were presented and discussed. Two hollow profiles within the same die were characterized by different thicknesses within the profile, two welding chambers and critical tongues (one fully supported and one partially supported). The material flow balance was performed by means of feeder size and position on a profile and by means of bearings on the other one. Accurate monitoring of process parameters was carried out by using a self-calibrating pyrometer for profile temperature, six thermocouples for die thermal monitoring, a laser velocitymeter for profile speed and two laser sensors for die deflection on critical tongues. AA6082 alloy was used as deforming material, while H-11 hot-work tool steel was selected for the die material. The experiments were repeated at least three times under the same conditions in order to provide a nearly steady state statistical distribution of the acquired data. These are used as a reference for the 2011 edition of the extrusion benchmark.
Authors: Ola Jensrud
Abstract: High strength aluminium alloys extrusions have successfully been applied for years in transportation industry. High strength alloys are normally understood to be alloys based on the Al-Mg-Zn system (7xxx) with addition of Cu in some cases and of course some micro structural controlling elements as Cr or Zr. The level of strength in the hardened condition (T6) is typical in the range from 320 to 500 MPa. The combination of strength and ductility of extrusions from the 7xxx series alloy gives several advantages in light weight construction and can contribute to lighter body and chassis in automotive. Significant improvements in extrusion speed are realized when the ratio Zn/Mg is increasing this means that alloys with high Zn and low Mg like 7108 and 7003 are favourable. Zr is the most promising element with respect to control the recrystallization phenomena. The fully understanding chemistry and the thermo-mechanical process route in profile based components manufacturing is concluded to be fundamental for high performance products.
Authors: Barbara Reggiani, Antonio Segatori, Lorenzo Donati, Luca Tomesani
Abstract: Although the extrusion process is regarded as a continuous process, in practice billets are discretely loaded into the press. The joining of two consecutive billets is guaranteed by the high hydrostatic pressure of the process. Nevertheless, mechanical proprieties of the profile in the welded region are lower than those of the adjacent area thus leading to the discarding of the welded segment. Extension of the segment is mainly affected by the interaction of seam and charge welding phenomena and, nowadays, its prediction is still a tricky task involving rough empirical relations or labour intensive analyses. Aim of this work was to identify the starting and exhausting points of the charge welds evolution inside an industrial multi-profiles die, in order to determine the exact position and the minimal length to be scraped. The extrusion of four AA6060 hollow profiles through a multi-hole die were preliminary monitored in an industrial press by accurate recording of the process loads, temperatures and speeds during the process. The four profiles were sectioned starting from the ‘stop mark’ then grinded and etched in order to investigate the location and the dimension of the zone to be ridded. While the experimental activity is detailed elsewhere, this paper is focused on the finite element modelling of the process. The numerical simulation was performed by means of the Altair HyperXtrude code and predictions compared to experimental data with a particular focus on the computation of the charge evolution. It was found a good agreement both in terms of general trend and prediction of the exhausting points so thus proving the code to be a reliable tool for an accurate determination of the scraps.
Authors: Matthijn de Rooij, X. Ma, A.J. den Bakker, Robert J. Werkhoven
Abstract: The surface quality of aluminium extrusion products can be hampered by undesired surface features like die lines and pickups. In particular the presence of pickups is considered as undesirable. Surface pickups appear as intermittent torn marks on the aluminium extrusion products, often terminated with a protruding lump rising above the surface up to hundreds of microns in height. Using a model calculating initiation, growth as well as detachment of the lumps on the die bearing surface, the surface quality of aluminium extrusion products can be predicted. The results of the model can be presented in terms of surface quality diagrams, where contour lines of the (normalized) calculated number of lumps are presented in terms of exit speed and extrudate surface temperature. These diagrams are unique for a certain combination of geometry of the extrudate and the aluminium alloy and can be used to optimise process conditions with respect to surface quality within a certain process window. In order to validate the model, the size and number of pickups on the surface of a labscale extruded strip of AA6063 have been measured. The results of the model are being compared to the experiments and show good agreement.
Authors: Sergey Stebunov, Nikolay Biba, Andrey Lishnij
Abstract: The paper presents the development of the Finite Element model for simulation of thin aluminium profile extrusion of both solid and hollow shapes. The analysis has shown that the material flow in simulation is very dependent on the friction model. Experimental and theoretical studies show that friction traction on the interface between the tool and the deformed material can be represented as a combination of adhesive friction force and the force that is required to deform surface asperities. In aluminium extrusion we can clearly distinguish two different areas with respect to friction conditions such as sticking and sliding and transient zones between them. The lengths of these zones are also dependent on variation of the choke angle and actual thickness of the profile. To get these values the material flow problem is to be coupled with the simulation of the tools deformation. A series of experiments with specially designed tools have been done to investigate how the bearing length and choke angle may influence the extension of different friction zones and by these means vary the material flow pattern. The friction models have also been tested with industrial profiles of complex shapes and have shown good correspondence to reality.
Authors: Tommaso Pinter, Mohamad El Mehtedi
Abstract: Constitutive equations relate thermo-mechanical parameters, i.e. strain (ε), strain rate (έ) and temperature (T), with flow stress (σ). The most popular constitutive relationship, among those used in the study of hot deformation, is the phenomenological sinh Garofalo equation. In recent years several papers described the hot deformation of aluminum alloys by mean of hot torsion testing. However, sinh constitutive parameters are seldomly available in literature even for the commonest aluminum alloys used today by the extrusion industry. This paper presents the result of the torsion tests providing constitutive equations for AA6005A, AA6063 and AA7020 alloys. The relative extrudabilities of these alloys were estimated by means of FEM simulation carried out by the HyperXtrude® software.
Authors: Michihiko Hoshino
Abstract: In Nihon University, Conform continuous extrusion and new extrusion processes which are called multi-billet extrusion have been investigated last ten years. Conclad extrusion which was developed from Conform continuous extrusion[1], is applied to manufacturing trolley wire for train in Japan. The trolley wire which is copper covered steel wire has shorter life cycle than expected one because of corrosion for acid rain. The quality of welding part of copper must be improved. In this paper, it is investigated how to decrease involving oxide films in welding part by experimental method. On the other hand, the multi-billet extrusion[2] is applied to manufacturing automotive frames, especially impact attenuators. The developed extrusion process has been done under experimental condition. However, it is capable to vary geometries of rib which is in the inside of closed profile extruded products by this process.
Authors: Bartłomiej Płonka, Juliusz Senderski
Abstract: The subject of the research was an alloy AlZnMg and AlCuMg with addition of Zr and Ag manufactured of powders by hot plastic consolidation in process of direct extrusion. Paper also presents results of research of structure evolution and mechanical properties for different tempers of precipitation strengthening and further plastic deformation, including hydrostatic extrusion. Obtained results Rm above 700MPa (for AlZnMg alloy) and above 500MPa (for AlCuMg alloy) shows significant possibilities of manufacturing from Al alloys powders products with ultrafine grain and nanometric structure which properties exceeding alloys manufactured with standard methods.
Authors: N. Grittner, B. Striewe, A. von Hehl, D. Bormann, M. Hunkel, H.W. Zoch, F.W. Bach
Abstract: The combination of different metallic materials enables the design of lightweight structures with tailor-made properties at global as well local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. Whereas titanium alloys show particular high mechanical strength and good corrosion resistance, aluminium alloys provide a considerable lower density and consequently higher potential for weight savings. However, after conventional fusion joining, e.g. after laser beam welding, heat affected zones, porosity or grain growth may occur and impair the local properties [1, 2]. In contrast, by solid-state joining techniques like co-extrusion these disadvantages can be avoided. Therefore co-extrusion exhibits an attractive solution for long products combining aluminium and titanium based alloys. Current investigations have been focused on the co-extrusion of aluminium and titanium, where titanium is the reinforcing element that is inserted in aluminium profiles. Two different billet variants were examined in the investigations, a titanium-core integrally moulded in the aluminium-billet and titanium-core inserted in a hollow drilled aluminium-billet. Experiments were made with different material combinations, Al99.5 with titanium grade 2 and AlSi1MgMn with Ti6Al4V. Beside mechanical properties of compound the formation of bonding zone are presented.

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