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

对创新轻质建筑的需求日益增长，需要使用镁作为建筑材料。通过不同的合金元素和制造工艺，可以稳定地提高镁的机械性能。特别是通过剧烈塑性变形处理来提高镁的机械性能是值得强调的。然而，在挤压或轧制后，由于镁的六方晶格结构和孪晶变形的必要性，镁根据压缩或拉伸（强度差异效应（Strength Differential Effect），σ）以及分别与挤压和轧制方向相关的载荷方向（各向异性）显示出屈服应力的差异。由于在现实中多轴应力条件下主要发生，所以弯曲和各向异性代表镁的缺点。为了扩大镁合金作为建筑材料的应用范围，掌握镁合金的变形和各向异性的基本知识是非常重要的。在该项目中，微观结构和最终的机械性能应通过创新的过程控制来操纵，一方面通过增加剪切应力分量，另一方面通过提高压缩应力分量。因此，剪切应力分量是建设性地提高ECAP变形的集成和通过在原来的压力机模具中的预腔。通过在挤压前对坯料进行锻造预处理，提高了压应力分量。

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.