Research On High Strain Rate Deformation Behavior Of 6016-T4 Aluminum Alloy Sheet

6000 series aluminum alloy is widely used in the manufacture of automobile body parts,and it is the preferred material for lightweight automobiles because of its excellent processing performance and corrosion resistance.The current research on this series of alloys mainly focuses on the quasi-static deformation behavior.However,in the actual production and use process,the material will inevitably be subjected to dynamic loads.Therefore,it is very important to study the mechanical behavior and microstructure changes of 6000 series aluminum alloys under high strain rate conditions.6016-T4 aluminum alloy sheet is the research object of this article.The split Hopkinson pressure bar equipment is used to achieve high strain rate compression deformation experiments in different directions,different strain rates and different strains,and to study the changes in the mechanical behavior of the material.The 6016-T4 aluminum alloy sheet exhibits weak positive strain rate sensitivity at strain rates of 1600 s^-1 and 2300 s^-1;it exhibits negative strain rate sensitivity when the strain rate increases to 3200 s^-1.The flow stress value of the specimen in the 0°direction during deformation is always greater than the 45°and 90°directions,and the45°direction has the lowest stress value.The sheet shows the characteristics of anisotropy.By analyzing the true stress-strain curve obtained in the high strain rate and quasi-static compression deformation experiment of 6016-T4 aluminum alloy sheet,the parameters required by the Johnson-Cook constitutive model are fitted.A constitutive model is established and improved to describe the changes in the mechanical properties of materials during the deformation process.The data calculated by the constitutive model is in good agreement with the experimental data.The established constitutive model is used as the material parameter to simulate the deformation process of the specimen through the ABAQUS finite element software,and the temperature field change caused by the adiabatic temperature rise of the specimen is analyzed.As the strain rate and strain increase,the temperature of the specimen also increases.Observed by a metallurgical microscope,the strip-shaped grains in the sheet before deformation are distributed transversely along the rolling direction.After the sheet is deformed at a high strain rate,the grains in the sheet undergo large deformation.As the strain rate and the amount of strain increase,almost all crystal grains are severely compressed.The crystal grains are gradually elongated and distributed longitudinally along the normal direction of the axis of the specimen.Through electron backscatter diffraction characterization,it is found that the crystal orientation of the sheet is mainly changed from<100>to<110>crystal orientation under the action of shearing force,and the texture intensity increases with the increase of strain rate and strain.Deformation texture and recrystallization texture are the main textures in sheet that have not undergone high strain rate deformation.After deformation,a large number of shear textures mainly composed of E,F and R-Cube textures are produced.By analyzing the distribution of misorientation,it can be seen that before the 6016-T4 aluminum alloy sheet is deformed,there are small-angle grain boundaries and large-angle grain boundaries between the grains,and the content of large-angle grain boundaries is about 90%.After the sheet is deformed at a high strain rate,the small-angle grain boundary content rises sharply.The sub-grain boundary content is as high as about 65%,and the high-angle grain boundary content is only about 27%,which shows that there are many sub-structures.Under the action of dynamic recovery,as the strain rate and strain increase,the content of small-angle grain boundaries decreases,the content of sub-grain boundaries drops to a minimum of 55%,and the content of large-angle grain boundaries increases to about 34%.