Investigation of 7A09 aluminum alloy prepared by continuous variable cross-section direct extrusion (CVCDE)

Preparation-forming is a common method to get high-performance alloy products, but lots of shortcomings exist in this method, such as complex and long process, high costs, and so on. As a new severe plastic deformation technology, continuous variable cross-section direct extrusion (CVCDE) is used to solve these problems. Taking 7A09 aluminum alloy, for example, the research result of CVCDE process shows that actual material flow distance is longer than conventional extrusion, and the axial stress on product surface in the die orifice is also significantly decreased. At the same time, the material flows through die cavity sequentially and suffers “upsetting-extrusion-upsetting” continuous loading, which will result in a severe deformation. By analysis of the microstructure and mechanical properties of 7A09 aluminum alloy was obtained under different conditions, it can be known that the grains become smaller and more round, and the uniformity gets also improved after CVCDE. Compared with conventional extrusion, the grain refinement of CVCDE with one and two interim dies increased by 22.4 and 41.5 %, respectively, and tensile strength and elongation also increase. To sum up, CVCDE with high efficiency, low consumption, short process, and other unique advantages in obtaining high-performance alloy products will be certainly raised wide concern.