Study On Deep Drawing Formability Of 6A16 Aluminum Alloy For Automobile Body Panel

With the increasing impact of global warming,cars with low energy consumption,low pollution and high fuel economy have attracted more and more attention from consumers.Lightweight of vehicle has become the development theme of the world automobile industry.Aluminum alloy has attracted extensive attention from scholars in terms of vehicle lightweight due to the advantages of low density,high specific strength and high specific stiffness.6xxx series aluminum alloy is applied widely in vehicles for its strong corrosion resistance,medium strength and good forming properties.In recent years,researchers have focused on the effects of different forming parameters on the overall forming properties of aluminum alloys.But they lacked the specific analysis of these effects from the aspects of microstructure and metal flow.6A16 aluminum alloy has fast aging response performance and good prospects in the application of automotive panels and also has been trial-produced in large quantities.In this paper,6A16 aluminum alloy is the research object and ABAQUS is used as the CAE software to simulate the deep drawing test.The metal flow and microstructure of various parts of the drawing process are observed and analyzed to understand the reasons for the macroscopic deformation and microstructure difference of the sheet during the forming process.The influence of forming parameters on the deep drawing of the sheet after parking at room temperature for different times is studied.The main research works and contributions are concluded as follows:The ABAQUS software simulation was used to simulate the deep drawing test.The results showed that the stress and equivalent strain of the cylindrical part were the largest at the top of the cylinder wall,the plate at the top of the wall was thickened,and the plate at the corners was thinned.The cylindrical member gradually becomes thinner from top to bottom along the cylinder wall,the top has the largest thickening rate,and the rounded corner region has the largest thinning rate.Ears are observed in four directions of 0°,90°,1800 and 2700 to the rolling direction.As the friction coefficient increases,the reasonable blank-holding force(BHF)interval becomes narrower.When the BHF increases,the stress and strain of the cylindrical member increase,and the thickening rate and thinning rate also increase.For the deep-drawn forming under the test conditions,the suitable forming speed interval is 5mm/min?45mm/min,and the suitable friction coefficient interval is 0.02-0.16.When the friction coefficient is 0.05,the suitable BHF range is 8-26KN.When the friction coefficient is 0.1,the appropriate BHF range is 10-22KN.When the friction coefficient is 0.15,the suitable BHF range is 6-12KN.The stress and strain of the cylindrical member increase as the friction coefficient and BHF increase.To verify the results of simulation,the deep drawing tests of 6A16-T4P aluminum alloy sheet are processed.The results show that,with the increase of the BHF and friction coefficient,the forming force increases,the top grain size becomes larger,the wall and fillet part of the grain size becomes smaller,and the hardness of the cylindrical part after drawing is also increased.As the forming speed increases,the stress and strain change in the deformation zone during the deformation process little.The microstructure and metal flow during deep drawing of 6A16-T4P aluminum alloy were studied.With the deep drawing of the blank,the grains of the top area first lengthen and then become larger,and finally present an equiaxed distribution with a grain size of about 36.4?m.The grains of the wall area grow at begin,and then are elongated along the drawing direction,the grain size is 26.3?m finally.The grain of the rounded area are gradually elongated along the drawing direction,and the grain size is gradually reduced,and the grain size is 23.1 ?m finally.As the deep drawing progresses,the Mg2Si phases of top area are gradually broken and become smaller due to large and complex deformation.And the second phases of the wall area are reduced in size.Meanwhile,the average size and number of the second phase of the rounded area vary little.The effect of room temperature parking on deep drawing of 6A16 aluminum alloy was investigated.The extension of the room temperature parking time increases the deep drawing force of the 6A16 aluminum alloy during the deep drawing process.And the influence of the BHF,the friction coefficient and the forming speed on the deep drawing test becomes more remarkable at the same time.The degree of deformation of the formed part is increased under the same forming parameters,which is manifested by an increase in the ear drop rate,a increase in the maximum thickening rate and the maximum thinning rate.The best forming parameters of 6A16-T4P aluminium blank are:BHF is 10KN,friction coefficient is 0.05 and the forming speed is 25mm/min.When the time of room temperature parking is 45 days,the deep drawing forming parameters are:the BHF is 10KN,friction coefficient is 0.05 and the forming speed is 25 mm/min.When the time of room temperature parking is 90 days,the deep drawing forming parameters are:the BHF is 14KN,friction coefficient is 0.1 and the forming speed is 15mm/min.The stamping forming process of 6A16 aluminum alloy automotive panel was studied.Combining the above-mentioned results of small-size deep drawing,the stamping forming process is derived,arid the stamping forming is successful.After 45 days of parking at room temperature,the suitable forming parameters for stamping forming of 6A16 aluminum alloy automobile cover parts are:the blank-holder pressure is 5MPa,friction coefficient is 0.05,and the forming speed is 25mm/min.Combined with the simulation and the analysis of the cover's surface quality and microstructure,the easily damaged location is judged.