| 6061 aluminum alloy is good plasticity, as well as excellent weldability and corrosion resistance. It can be processed to plates, tubes, rods, types, wires, and forgings. It can be used to profiles for architecture and large sized structure components, truck, automobile, ship, rolling stock, catheter, which need excellent corrosion resistance. At the same time, because of its low density, excellent energy conservation and environmental protection, it becomes one of the most excellent materials. So how to improve its performance to satisfy the demands of developing industrial production, become hotspot in various fields.Grain refinement is an effective method of improving material strength. The results show that, when grain refine to 1μm, materials will exhibit a series of unwonted performance, such as physical, chemical, and mechanical. There are several methods to make ultra-fine grain materials. But severe plastic deformation gets more and more focus because of its merits of preparing dense bulk material with simple craft and little cost. During equal channel angular pressing(ECAP) process, grains of the severe deformed materials are greatly refined. Increasing interests have been focused on ECAP techniques that can process that their properties will be different from, and often superior to those of conventional coarse-grained materials. Researching of preparing ultra-fine grain materials with CCDC is in primary stage. The result of conventional grain size refining to submicron size even nanometer size with CCDC is better than other methods. In this paper, on the based on the previous research of our research group raised the CCEC that combined advantages of the two methods, it is evolved two types of process route and presents a composite extrusion process, preparing ultra-fine grain materials with composite extrusion severe plastic deformation to 6061 aluminum alloy.According to characteristics of composite extrusion process, it is processed tomaterial by composite extrusion processing, and ECAP process in terms of performance, the evolution of organizations to do detailed comparison.this paper presents two different process routes to do composite extrusion processing and compare with equal channel angular extrusion process. At room temperature, experiment successfully finished 4pass composite extrusion processing to 6061 aluminum alloy. Research microstructure, tensile properties, and micro-hardness of 6061 aluminum alloy in the three different process routes. And compare each other with different processing pass. Observation of microstructure show that process routes of CCDC-ECAP is the best in grain refinement; Equiaxial grain-refining which grain or domain size is less than 1μm can be received after 4pass composite extrusion processing; Finally refinement degree of grain depends on size of grain, extrusion process deformation, and recrystallization annealing technology before composite extrusion; This process routes can receive the best mechanical properties (strength, microhardness, yield strength), but its elongation is relatively low.Try different recrystallization annealing system, and analysis the regularity of microstructure evolution in different recrystallization annealing technology. Under different deformation, determine the annealing technology which can both eliminate work hardening, and product homogeneous small grain. And provide evidence for parameters of further study or industrial production.Research relationship between materials deformation with deformation texture by composite extrusion processing and ECAP process. The results show that ECAP deformation has a stable texture when shearing deformation is continuously increasing. To 6061 aluminum alloy, the tests indicate that rotation cube texture can be formed in materials under the relatively small deformation. However, with increasing of ECAP deformation and decreasing of strength about rotation cube texture component, the strength of{112}<110> component increases rapidly, and it becomes the only texture component in materials. So there are a metastable rotation cube texture and two stable{112}<110>A texture and{111}<110>Z texture component with increasing of ECAP deformation. Composite extrusion process includes extrusion shearing and compression bending deformation. In the compression process, except rotation cube texture, there is a {112}<110>texture component. With increasing of process passes, rotation cube texture component decreases, and there are relatively stable{112}<110>,{423}< 112>,and {112}<111> texture component.A bit amount of{123}<634> S texture and the very weak U{100}<001> texture orientation also exist.To 6061 aluminum alloy which can be heat treatment strengthened, the materials after deformation may do heat treatment such as recrystallization annealing process in application. So researching high temperature stability of fine grain structure in materials after composite extrusion process, and the change of texture in annealing process, are also main contents of this paper. To 6061 aluminum alloy, the results show that materials have excellent thermal stability after ECAP deformation. Grain tended to homogeneous and size unchanged after annealing 0.5h under 300℃. The main texture of 6061 aluminum alloy is a rotation cube texture after ECAP deformation and annealing 1h under 180℃, and is a stable cube texture after annealing 300℃×0.5h. To different from ECAP deformation and annealing, Annealing of aluminum alloy after composite extrusion process, Its recry stallization texture has decreased with the temperature increasing cube texture{100}<100> component.and the form-ation of recry stallization twin-oriented B{110}<112> texture component. Around the TD/<111> rotation in the matrix is formed twin. Texture analysis of the above results, the next step in-depth to study composite extrusion deformation mechanism provides an important basis. |
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