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The design of extrusion dies depends on the experience of the designer. After the die has been manufactured, it is tested during an extrusion process and machined several times until it works properly. The die is designed by a trial and error method which is expensive interms of time consumption and the amount of scrap. Research is going on to replace the trial pressing with finite element simulations that concentrate on material and tool analysis. In order to validate the tool simulations, an experiment is required for measuring the deformation of the die. Measuring the deformation of the die is faced with two main obstacles: high temperature and little free space. To overcome these obstacles a method is tried, which works by applying a laser beam on a reflecting surface. This cheap method is simple, robust and gives good results. This paper describes measuring the deformation of a flat die used to extrude a single U shape profile. In addition, finite element calculation of the die is performed. Finally, a comparison is performed between experimental and numerical results.

Insight in the aluminium extrusion process can be gained with numerical simulations. This paper gives an overview of the research done to model aluminium extrusion with the Arbitrary Lagrangian Eulerian (ALE) FEM code DiekA. The ALE formulation is used to avoid mesh distortion, which is a major problem in the simulation of extrusion. The goal of this research is to increase the lifetime of extrusion dies and to decrease the number of corrections necessary to these dies. To model the rate-dependent behaviour of hot aluminium, normally a viscoplastic material model is used. However in the bearing the material behaviour is mainly elastic. The pressure and friction in the bearing are dominant factors in the extrusion process and an accurate modelling of this area is crucial for the final results. In this paper an elasto-viscoplastic material model is derived. This models can be simplified to a very efficient model that is elasto-viscoplastic for small deformation increments and viscoplastic for large increments. With this model it is possible to model the extrusion process including the elastic behaviour in the bearing without sacrifising efficiency. As an example the extrusion of a tube is treated. To avoid unacceptable calculation times, the simulation is split into three parts. First a detailed 2D simulation of the bearing area is made. The results of this simulation are used in a complex 3D simulation of the aluminium flow true the die. From this simulation, the loads on the die are determined. These loads are used in a stress analysis of the die. The results of these simulations give insight in the processes that occur in the aluminium and in the die.

Low density Al-4Mg-1.3Li-0.4Zr and Al-6Mg-1.6Li-0.4Zr alloys were spray formed and the billets extruded under a range of conditions. The alloy compositions were selected to provide an attractive balance of tensile strength and elongation, without relying on complex post-processing and heat treatments -and are therefore suitable for complex cross section extrusions and free from quench distortion. The as-spray formed microstructures showed fine homogeneous, equiaxed grains with an average size of 10 -15 lm. Firstly, a laboratory scale extrusion was carried out to extrude 30 mm diameter billets into 7.5 mm diameter cross-section and to investigate the effects of temperature and ram speeds on microstructural development. The microstructure after extrusion at 400 8C was partially dynamically recrystallised with a l0.5 area fraction of l1 lm grains and the remainder were unrecrystallised elongated grains. Electron backscatter diffraction showed a mixed a111A + a100A double fibre texture. After peak age hardening at 150 8C for 96 h, the Al-6Mg-1.6Li-0.4Zr alloy showed a 0.2% proof strength of 495 MPa, a tensile strength of 553 MPa and elongation to failure of 8.5%; Al-4Mg-1.3Li-0.4Zr showed a 0.2% proof strength of 392 MPa, a tensile strength of 476 MPa and an elongation of 10%. Subsequently, large-scale complex cross-section were extruded at l400 8C. Due to the complexity of the cross-sections and the non-axisymetric deformation, the fibre texture was distorted to FCC rolled Copper and Brass orientations. After a dual-step age hardening treatment of 130 8C for 8h followed by 160 8C for 8h, the proof strength, ultimate strength and elongations were 340 MPa, 470 MPa and 16% respectively. The combination of relatively simple process steps, high strength and ductility/formability, and low distortion in complex sections demonstrated the strong potential for these low density alloys in aerospace and autosport applications.

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