| Aluminum alloy has been widely used in aerospace,high-speed rail transit and other fields due to its advantages of light weight and high strength.6005A aluminum alloy has good plasticity,machinability,weldability,corrosion resistance and hot extrusion properties.And it has some price advantage.Therefore,it is often used to manufacture the structural parts of high-speed rail,ship,aircraft and other large equipment.With the increasing requirements of high performance,lightweight and precision forming,large cross-section,large wall thickness difference and asymmetric multi cavity aluminum alloy profiles have become the key structural profiles for aerospace,high-speed rail transit and other projects.And this kind of profile has high forming accuracy and mechanical properties requirements,which brings technical challenges to the selection of extrusion process parameters and die structure design.Therefore,it is of great significance to research the extrusion technology of large complex cross-section multi cavity profile for improving the overall level of aerospace,high-speed rail transit and other high-end equipment manufacturing industry.In this thesis,6005A aluminum alloy profiles for a certain aircraft cabin are researched.The plastic deformation behavior of the alloy at different temperatures and strain rates was researched.The constitutive model and thermal processing maps of the alloy were established.The extrusion die of large complex cross-section multi cavity profile for cabin was designed.The numerical simulation model of extrusion process was established.The flow law of metal during extrusion was analyzed.The die structure such as baffle plate,welding chamber,bearing and porthole was optimized to improve the flow velocity uniformity of the profile section at the die outlet.The influence of extrusion parameters on microstructure,coarse grain layer and mechanical properties of 6005A aluminum alloy profile were researched.The main research contents and achievements of this thesis are as follows:(1)The hot compression tests of 6005A aluminum alloy were carried out under the conditions of deformation temperature 623?823K and strain rate 0.01?10s-1.The stress-strain curves at different temperatures and strain rates were obtained,and the flow behavior of the alloy was analyzed and revealed.By modifying the deformation temperature and friction,a high-precision Arrhenius constitutive model considering strain compensation and the thermal processing maps under different strains were established,and the optimum range of thermal processing parameters of the alloy were determined.(2)The 6005A aluminum alloy profile with large cross-section and complex hollow for a certain aircraft cabin is taken as the research object.The extrusion process parameters of the profile are analyzed and determined,and the structure of the porthole extrusion die is designed.Based on the HyperXtrude numerical simulation software and the established constitutive model,the numerical simulation model of the profile porthole extrusion process was established.The influence of different extrusion process parameters on the profile extrusion deformation was researched,and the reasonable extrusion speed was determined.(3)The influence of different die structures on the material flow velocity uniformity of the profile section at the die outlet was studied,and the structure of the die baffle plate,welding chamber,bearing and porthole were optimized.Then,based on response surface method,the optimization design modelcf extrusion die for cabin profile was established.The influence of the height of the baffle plate,the inclination angle of the first welding chamber and the ratio of the depth of the second welding chamber to the depth of the first welding chamber on the forming quality of the profile were studied.Through the above,the optimal die structure is determined.The numerical simulation model of extrusion die strength analysis was established,and the strength of extrusion die was checked.(4)In order to research the influence of extrusion process parameters on the microstructure and mechanical properties of 6005A aluminum alloy extrusion profile,an extrusion experiment of I-section profile was carried out.The differences of mechanical properties,microstructure and thickness of coarse grain layer at different positions of I-section were systematically studied.The influence of extrusion process parameters on microstructure,coarse grain layer and mechanical properties of 6005A aluminum alloy profile was also studied.The combination of extrusion process parameters to effectively control the thickness of coarse grain layer and its mechanical properties was determined. |
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