Reseach On High Strain Rate Deformation Structure And Performance Of AA3003 For Automotive Battery Shell

Aluminum alloy is one of the important materials used in automobile lightweight applications.AA3003 is an Al-Mn series,non-heat treatment strengthened aluminum alloy,which has the advantages of high specific strength,corrosion resistance,good thermal conductivity and so on.It has been widely used in the production of automobile parts.At present,there are few researches on the mechanical properties of AA3003 at high speed,and no more accurate constitutive model can describe the mechanical behavior of this kind of material in the range of large strain rates.Therefore,the mechanical properties of AA3003 in as-received and different rolling reductions（20%and 40%）states at room temperature were studied systematically in this paper.Meanwhile,the Johnson-cook constitutive model with high prediction accuracy is established.The microstructural evolution of AA3003 was observed by means of POM,SEM,EDS and TEM,and the relationship between microstructure and mechanical behavior was discussed.At the same time,the concepts of scratch influence coefficientand rangeare introduced to analyse the influence of scratch depth and direction on the mechanical properties of materials under dynamic load.The fracture behaviors of specimens with different scratch directions are revealed through macroscopic fracture observation,in order to obtain references for the design,development and application of AA3003 in a wide range of use.The results show that the yield strength,tensile strength,fracture elongation and strain energy density of the as-received and rolled AA3003 increase with the increase of strain rate.With increase of rolling reduction,the yield strength and tensile strength of AA3003 increase,while the elongation and plasticity decrease.Considering the coupling effect of strain and strain rate on rheological behavior,the J-C model is modified.The statistical method shows that the predicted value of J-C model is more correlated with the experimental value.From quasi-static(10^-3/s)to high strain rate（1000/s）,AA3003 is ductile fracture.At high strain rates,the dimples of fracture become larger and deeper,and the density is increased.With the increase of rolling reduction,the number of dimples decreased,dimples became shallow,and the proportion of shear plane increased.The TEM images shows that with the increase of rolling reduction and strain rate,the dislocations increased.Moreover,the dislocation wall,dislocation cell and sub-crystals structures are observed.With the increase of scratch depth,the yield strength,tensile strength and fracture elongation of AA3003 decreased.With the increase of the angle between the scratch and the tensile direction,the influence of the scratch on the mechanical properties of the specimen increases.The macro fracture of the specimen with parallel scratch to tensile direction shows necking phenomenon,which is ductile fracture;the specimen with 45°and vertical scratch to tensile direction changes into shear fracture,with lower plasticity.