| Hyundai cars continue to pursue lightweight and safety,especially car safety,which is an eternal topic around people.Automobile safety parts made of traditional steel have poor energy absorption per unit mass,which no longer meets the requirements of automobile safety parts.The 7000 series aluminum alloy has the advantages of low density,high specific strength,specific rigidity,etc.,and has a significant application background in automotive safety components.This paper adopted the metallography,SEM,EBSD and TEM,hardness,and tensile performance test methods such as system to study the solid solution and aging process on microstructure and mechanical properties of 7003 aluminum alloy extrusion profiles,the influence of by the axial crushing test shows the relationship between material mechanical properties and the crushing performance and analyzes the microstructure of aluminum alloy thin-walled beam cracking behavior.The main research contents and conclusions of this paper are as follows:The effects of different solution treatments on fiber structure,mechanical properties,and new crushing properties of aluminum alloy extruded materials were studied.The results show that the in-line solution aluminum alloy profile is dominated by the fibrous crystal structure,the recrystallization fraction is only 6.9%,and the crushing absorption energy is 33.3k J.In the off-line solution at low temperature(450?,470?),with the extension of solution time,the recrystallization fraction increases gradually,the strength of the alloy decreases,and the crushing energy absorption decreases gradually.In the off-line solution at 490?,with the extension of solution time,the recrystallization fraction increased significantly,the second phase of Zn and Mg began to dissolve,and the properties of the alloy increased gradually,but the plasticity,toughness,and energy absorption of the collapse decreased somewhat.2)The precipitation behavior of in-line solution 7003 aluminum alloy extruded parts during the aging process of T6,T79,T74,and T73 were studied.The results show that after T6 aging treatment,the strengthening phase of the aluminum alloy is mainly ? 'phase,the size is small and the dispersion distribution and the strength reaches the peak.After the two-stage aging treatment,with the extension of aging time,the precipitates gradually grow up,part of ? 'phase into ? phase,and the number of the precipitates gradually increases,the distribution density decreases,the strength of the alloy decreases,and the toughness increases.After T6 aging treatment,the crushing and absorbing energy of the aluminum alloy profile is 27.2k J,and after T73 aging treatment,the crushing and absorbing energy of the aluminum alloy profile is33.3k J,which is 22.4% higher than that of the T6 state.3)The influence of the microstructure of aluminum alloy profiles on cracking behavior during axial deformation is analyzed.Aluminum alloy profiles are prone to cracking of high recrystallization degree,in the process of compression deformation,the crack in the coarse grain of aluminum alloy profile edge initiation and continue to expand,the deformation of fiber has the obvious inhibiting effect of crack propagation,with the increase of the degree of recrystallization,crack extension along the recrystallization grain boundary,therefore more prone to cracking.After T6 aging treatment,the precipitates at grain boundaries are continuously distributed,which provides favorable conditions for crack propagation.After two-stage aging treatment,the spacing between precipitated phases increases and the intergranular cracking tendency decreases. |
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