| 7075-T6 aluminum alloy has the advantages of high strength and corrosion resistance,and is widely used in the manufacturing of structural parts in the aerospace field.However,high strength aluminum alloy is easy to crack at room temperature,so hot forming is the main method to improve the formability of refractory materials.Electromagnetic forming can improve the forming limit of difficult-to-deform materials,but the existing technology is mainly applied to low strength aluminum alloy materials,and there are few studies on the dynamic deformation law and properties of 7075-T6 high strength aluminum alloy.In this paper,the dynamic deformation behavior and the relationship between microstructure and properties of 7075-T6 aluminum alloy during electromagnetic hot forming at different temperatures were studied by using finite element simulation and macro and micro experiments.The main research contents and conclusions are as follows:(1)The multi-physical field coupling model of electromagnetic field,structure field and temperature field of 7075-T6 aluminum alloy sheet metal in electromagnetic hot forming process was established.Based on Python language,a user subroutine for interactive iteration of simulation results between ANSYS and ABAQUS software is developed to realize automatic transmission of coupling variables calculated by different simulation software,which significantly reduces labor cost and improves efficiency.(2)The effects of forming temperature and coupling algorithm on forming height and deformation profile were analyzed by using multiphysical coupling model.When the forming temperature increases from 25℃to 200℃,the electromagnetic force on the sheet decreases significantly while the yield strength does not,which results in the decrease of the forming height of the sheet.When the temperature increases from 200℃to 400℃,the deformation resistance of the sheet metal decreases significantly while the electromagnetic force decreases slightly,resulting in the forming height of the sheet metal increases gradually.Compared with the experimental results at different temperatures,it is found that there are obvious errors in the forming height and deformation profile obtained by the loose coupling method.The sequential coupling method has high precision and the maximum height error is less than 7%.(3)The dynamic deformation of 7075-T6 aluminum alloy sheet under electromagnetic forming process was analyzed by finite element method.When the forming temperature is 25℃ and the voltage is 5k V,the yield strength of the material is large,which leads to the violent shaking of the sheet metal during the forming process,and the final deformation profile and equivalent plastic strain distribution are wave shape.Compared with25℃,the yield strength of the sheet decreases significantly at 400℃,the maximum forming height increases by 70.4%,the sheet does not shake significantly during the deformation process,and the final deformation profile and equivalent plastic strain are evenly distributed.(4)The mechanical properties and forming limit of 7075-T6 aluminum alloy electromagnetic hot forming sheet were studied.Compared with 300℃,dynamic recrystallization and grain refinement occurred at 400℃,and mechanical properties were improved.The yield strength of the sheet metal is 256 MPa after electromagnetic hot forming at400℃.The tensile strength and yield strength of the sheet metal are up to552 MPa and 471 MPa after solid solution quenching at 475℃ and artificial aging at 120℃.After electromagnetic thermoforming and solution aging,the hardness and elongation of 7075-T6 aluminum alloy reach 98.9% and113.3% of the original state,respectively.Compared with 25℃electromagnetic forming,the forming limit of 400℃ electromagnetic forming material is increased by 77.7%,and compared with 400℃ quasistatic stamping,the forming limit of 400℃ electromagnetic forming material is increased by 45.3%.Compared with the normal temperature electromagnetic forming and hot stamping forming process,the forming limit of 7075-T6 aluminum alloy sheet metal under electromagnetic hot forming process is significantly improved. |
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