Reduction of anisotropy and the SDE of magnesium profiles by means of a specific process control of the extrusion process

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The increasing demand for innovative lightweight construction requires the use of magnesium as a construction material. By means of different alloying elements and manufacturing processes the mechanical properties of magnesium could be steadily increased. Especially the increase of the mechanical properties of magnesium by the treatment with severe plastic deformation is to be emphasized. However, after extrusion or rolling due to its hexagonal lattice structure and the necessity of twinning to deformation, magnesium shows distinctions in yield stress according to compressive or tension (Strength Differential Effect, SDE) as well as the direction of loading in relation to the extrusion and rolling direction respectively (anisotropy). Since in reality multiaxial stress conditions predominantly occur, the SDE and the anisotropy represent a disadvantage of magnesium. In order to increase the range of application of magnesium alloys as a construction material basic knowledge of manipulation of SDE and anisotropy are of great importance. In this project the microstructure and finally the mechanical properties should be manipulated by an innovative process control, on the one hand by an increase in the shear stress components, on the other hand by an elevation in the compressive stress components. Thereby the shear stress component is constructively elevated by integration of ECAP deformation and by pre-chambers in the original press die. The compressive stress component is enhanced by the pre-treatment of the billet by means of forging before extrusion.