Dynamic Compression Deformation Behavior Of 6013 Aluminum Alloy

Because of its advantages of low density,high specific strength,excellent formability and corrosion resistance,aluminum alloy has been widely used in the manufacturing of car body parts,meanwhile it has become the first choice material for automotive lightweight.6013 aluminum alloy,as a new type of Al-Mg-Si-Cu aluminum alloy developed by Alcoa Corp,has good comprehensive properties,but the research on the alloy is mainly focused on the deformation behavior under quasi static condition,and the study on the mechanical behavior and microstructure evolut ion of the alloy under dynamic compression is rare.However,in practical applications,the material will inevitably bear dynamic load,so it is necessary to study the dynamic mechanical properties and microstructure evolutions of 6013 aluminum alloy under high speed impact.In this thesis,6013 aluminum alloy was taken as the research object.The mechanical behaviors of the alloy under different strain rates and different deformation temperatures were studied by the high speed impact test of Hopkinson pressure bar.The optical microscopy and transmission electron microscope devices were applied to characterize the microstructure evolution mechanism during compression deformation.The main research achievements of this thesis are as follows:(1)Compared with other solution and aging conditions,the result of solution strengthening and aging hardening of extruded 6013 aluminum alloy for solution treatment of 1 hour at 545 ? and aging treatment of 8 hours at 180 ? is the best,meanwhile the precipitates in the matrix is of great number with a homogeneous distribution.During dynamic deformation,the pinning effect for dislocation of the precipitates under this solution and aging condition is strong,the dislocation density increases,therefore,the alloy has high deformation resistance and shows strong positive strain rate sensitivity.(2)The extruded 6013-T4 aluminum alloy exhibits obvious mechanical anisotropy under dynamic load at room temperature.The 0° specimens have the highest flow stresses and show the strongest positive strain rate sensitivity.The 45° specimens have the lowest flow stresses and the strain rate sensitivity of them is weak.During high speed impact deformation,the effect of the strain and the strain rate on dislocation microstructure is significant,the dislocation density is positively correlated with the strain and the strain rate respectively.At the same time,the dislocation density of 6013-T4 aluminum alloy in the direction of 0° is very high,and the dislocation tangle is remarkable,thus the 0° specimens have the ideal strain hardening and strain rate strengthening effect.(3)When deformed at temperatures ranging from 25 to 400 ? under dynamic compression,the extruded 6013-T4 aluminum alloy shows weak positive strain rate sensitivity and strong negative temperature sensitivity.The microstructure observation of transmission electron microscope shows that deformation temperature has a significant effect on dislocation microstructure,and the dislocation density decreases with the increase of deformation temperature.When the temperature reaches 300 ?,the dislocation cell wall begins to exhibit polygon phenomenon and form subgrains.With the further increasing of temperature,the grain structure is broken due to the formation of a large number of subgrains.Based on experimental data,the Johnson-Cook constitutive model of 6013-T4 aluminum alloy is established,and the fitted flow stresses of this model are in good agreement with the experimental results in a wide range of strain rates and temperatures.