Dynamic Mechanical Response Behavior And Microstructure Evolution Of 7003 Aluminum Alloy Rolled Plate

The rapid development of the automobile industry has greatly promoted the stable growth of our economy,but also caused more and more serious problems such as environmental pollution,energy consumption and traffic safety.Lightweight can not only effectively reduce automobile fuel consumption,increase enterprise points,achieve good and rapid development of enterprises,but also an important way to achieve our carbon peaking and carbon neutrality goal.Aluminum alloy is one of the most ideal lightweight materials for automobile because of its excellent energy absorption,specific strength and corrosion resistance.Based on Hopkinson high-speed impact,the dynamic mechanical response behavior and microstructure evolution of 7003 aluminum alloy were systematically studied in the present work.The microstructure evolution of 7003 aluminum alloy in the process of dynamic impact deformation was discussed,and a dynamic mechanical constitutive model was established to provide theoretical and data support for the application of 7003 aluminum alloy in body impact structure.The following research contents and conclusions were drawn.(1)The as-cast and rolled 7003 aluminum alloy exhibit completely different mechanical response behavior under dynamic impact load.The flow stress of ascast 7003 aluminum alloy increases with the increase of strain rate,showing an obvious positive strain rate sensitivity.When the strain rate increases to 4100 s-1,the flow stress decreases with the increase of strain.The stress response behavior of rolled 7003 aluminum alloy is insensitive to strain rate when it is impacted along ND,RD and TD at high speed.The flow stress of 7003 aluminum alloy decreases with the increase of deformation temperature.(2)Based on the original JC constitutive model,a modified JC constitutive model was constructed by optimizing the strain hardening term and the strain rate coefficients C and n.The deviation between the constitutive fitting results and the experimental stress of as-cast and rolled 7003 aluminum alloy is within ±10%.The correlation coefficient(R)and average absolute relative error(AARE)of ascast 7003 aluminum alloy are 99.17%and 1.3%,respectively.The correlation coefficient(R)and average absolute relative error(AARE)of rolled 7003 aluminum alloy are 94.76%and 2.15%,respectively,indicating that the constitutive method can accurately predict the flow stress of as-cast and rolled 7003 aluminum alloy at different strain rates.(3)The mechanical properties of rolled 7003 aluminum alloy have obvious anisotropy under dynamic impact load.The flow stress in ND direction is the highest,RD direction is the second,TD direction is the lowest.With the increase of strain rate,the flow stress difference between TD and ND direction decreases gradually.The rolled 7003 aluminum alloy shows different microstructure evolution characteristics when the high speed impact deformation is carried out in different directions.The adiabatic shear band shows obvious anisotropy and is closely related to the grain morphology.The flatter the grain is,the more easily adiabatic shear bands are generated.(4)Impact deformation temperature significantly affects the microstructure evolution of rolled 7003 aluminum alloy.Dislocation density increases first and then decreases with the increase of deformation temperature.When the deformation temperature is 100℃,the ambient temperature combined with the adiabatic temperature rise is still not up to the critical recrystallization temperature,and the thermal activation is weak.Dislocation proliferation is the dominant mechanism of plastic deformation.With the increase of deformation temperature,the vacancy concentration in the alloy will continue to decrease,which makes the resistance of dislocation movement become smaller,and a large number of dislocation intertwine with each other to form dislocation cells,resulting in the cancellation of each other.At this time,the dislocation cells gradually polygon and form small-angle subgrains,which interact with the dislocation and evolve into recrystallized grains.