| The airline light alloy has been widely used in the manufacturing industry of aerospace equipment. It usually works in some extreme conditions such as high temperature, high vacuum, high pressure, intense radiation. In order to satisfy the strict requirements on the material properties from the operating environment. Some special grain refinement process was used to change the internal organizational structure of light alloy to improve the overall performance of the material. In this paper, equal channel angular pressing(ECAP) technology was applied to refine internal grain of light alloy materials- aluminum alloy 7475 to enhance the material strength, toughness, plasticity and overall mechanical properties.Lead was taken as prototype material under normal temperature conditions early. High temperature environment was replaced by the low temperature. The metal materials that easy deformation was used to study that difficult to deformation. Simulation method by the combination of numerical simulation and physical simulation was used to verify the feasibility of the ECAP process and programs. With the increasing number of extrusion, extrusion load increased, work hardening phenomenon was more obvious; The maximum load of each pass of the physical simulation experiments larger than that of numerical simulation, because that the friction hinder between the lateral punch and the residual lead of the channel wall during the extrusion process of the actual experiment can’t be obtained by the numerical simulation. According to the experimental program and procedures of the simulation, data and images were obtained to guide the research of ECAP technology of aluminum alloy 7475 in the high-temperature. The simulation method can predict some unknown factors existing in the actual production and operation, better guarantee the reliability and accuracy of experiment process.In addition to completing the extrusion process, the study of ECAP experiment for aluminum alloy 7475 in high temperature also need to test the grain size and mechanical properties of the material. The whole extrusion process referenced to the process of simulation experiment and conclusions of the lead. The equal channel angular extrusion accrued in the constant temperature of 420 ℃, with the extrusion speed of 2mm / sand the flip angle of 90 °. The materials were removed after 4 times repeated extrusion in the channel. The load changing trend in the extrusion process was the same with the simulation experiment results of the lead, with vertical strip and very rough scratches on the surface of the specimens, accompanied by serious burrs and barbs on the exit, in the form of an elongated and lacerated. Specimens were prepared by milling and chemical processing after machining. Optical microscope was used to observe the organizational structure, and the grain size of the internal organization of the materials before and after the equal channel angular extrusion in high temperature was calibrated. The comparison shows that the grain structure of materials after ECAP is less than the original one. finally, the experimental method of high temperature super plasticity based on maximum m value was used in the temperature range from 420℃ to 515℃ to detect whether the plasticity of aluminum alloy7475 improved or not, and find out the maximum deformation temperature of elongation.The above experiments show that high-temperature ECAP method allows the grain refinement of internal organization of aluminum alloy 7475, microstructure and properties of materials also changed. With the increasing number of extrusion, extrusion load increased, work hardening phenomenon is more obvious. The average grain diameter of aluminum alloy 7475 after ECAP at a temperature of 420℃ is 8μm, smaller than the original grain size; the using of high temperature super plastic tensile experiments based on the maximum m value, allow the elongation rate of aluminum alloy 7475 after grain refinement reached the maximum of 346.7% in 470℃, increase by 37.8%. |
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