| With the development of the country's economy and society,especially the tremendous progress of the automobile industry,the number of domestic cars in China is growing rapidly.The popularity of automobiles has brought comfort and convenience to our travels,and it has also brought great challenges to the rapid consumption of fossil energy and air pollution.Research shows that lightweighting is one of the effective ways to achieve energy saving and emission reduction targets in the transportation industry.In recent years,new energy electric vehicles have developed rapidly in China.Due to the use of a large number of battery packs to power the vehicle,the overall vehicle weight of the electric vehicle is increased,and the cruising range particularly concerned by the electric vehicle is severely restricted.Therefore,the lightweight of automobiles is particularly important in the development of traditional fuel vehicles and emerging electric vehicles.Due to its low density and high strength,high-strength aluminum alloys have great potential for reducing the weight of the entire vehicle in the automotive industry.At room temperature,the elongation of the aluminum alloy is low,making it difficult to form complex parts.With the mature application of hot stamping process in high-strength steel materials,the hot stamping process of aluminum alloy has received great attention.Although the hot stamping process can improve the formability of the aluminum alloy and reduce the springback of the formed parts,the high temperature friction and wear of the aluminum alloy always affects the surface quality of the formed parts and the service life of the mold.Therefore,it is very meaningful to study the friction and lubrication behavior of aluminum alloy sheets at high temperatures.In this paper,7075-T6 high-strength aluminum alloy sheet was selected as the research object,and the friction and lubrication behavior at high temperature were studied.The main contents of the study are as follows:Study on the high-temperature friction behavior of 7075 aluminum alloy under non-lubricating conditions: Firstly,the original high temperature friction tester was improved to improve the accuracy of friction factor measurement,and the relevant experiments under non-lubricating conditions are carried out by this testing machine.The friction factors under different process parameters were measured,and the surface morphology of the sheet and the mold after rubbing were observed by super depth of field and field emission electron microscopy to analyze The friction mechanism.Study on the high-temperature friction behavior of 7075 aluminum alloy under lubricating conditions: The experiment was carried out under the condition of lubrication by the self-made high-temperature friction tester.The friction factors under different temperatures and lubricant conditions were measured,and the improvement effect of the lubricant on the friction behavior was analyzed.The temperature and lubricant suitable for hot stamping of aluminum alloy were selected to prepare for the hot stamping test of forming anti-collision beam.Test of anti-collision beam for hot stamping of 7075 aluminum alloy sheet: According to the temperature and lubricant selected in the high-temperature friction experiment under lubricating conditions,the hot stamping forming test of the anti-collision beam is carried out to observe the thinning and cracking defects of the anti-collision beam and the friction marks on the surface.Comparative analysis of the effects of different temperatures and lubricants on the friction behavior and forming properties of anti-collision beams during hot stamping.This thesis mainly studies the friction and lubrication behavior of 7075 aluminum alloy at high temperature,aiming to provide certain experimental basis and process guidance for the production and application of 7075 aluminum alloy hot stamping process. |
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