Research On Preparation Technology Of High-strength Cast Aluminum Alloy For Large Wheel

Under the current policy background of tightening fuel economy regulations,lightweighting has become one of the important trends in the automotive industry.Large cars have less than 5%of the vehicle's ownership,while oil consumed accounts for 40%of the car.Wheels,as an important component of automobiles,are particularly important for car weight reduction.At present,large-size vehicles mostly use steel hubs or forged aluminum hubs.Steel hubs are not conducive to energy conservation and emission reduction.Forged aluminum hubs have higher costs,while low-pressure cast aluminum alloy hubs are lower in performance than forged aluminum alloy hubs,but by optimizing the composition of the alloy,subsequent melt treatment,casting process,heat treatment and other processes to improve rationally,to maximize the potential of low-pressure casting aluminum alloy wheels,so as to obtain higher mechanical performance of large trucks or passenger cars with large wheels,has gradually become domestic and foreign Production of large aluminum alloy wheels.Based on the commonly used cast aluminum hub A357 cast aluminum alloy components,the combination of the JmatPro simulation software and the experimental study was used to optimize the added Cu composition.The effect of different Cu content on the mechanical properties and microstructure of the alloy was studied.It was found that in the Al-7Si-0.5Mg alloy,the eutectic structure aggregates with the increase of Cu content,and the Cu element is mostly concentrated in the eutectic structure region,porosity and other defects in the alloy are also increased;with the increase of Cu,the tensile strength and yield strength of the alloy peak at 1.0 wt%,and the hardness of the alloy is also increased,but the plasticity decreases with the increase of Cu,so the appropriate amount of Cu added is 1.0%.The post-alloy composition was Al-7Si-1Cu-0.5Mg.Based on the optimization of composition design,the melt processing of Al-7Si-1Cu-0.5Mg alloy was studied.The ?-Al and eutectic silicon in the alloy were modified by new refiners Al-5Ti-B-1RE and Sr,respectively.On this basis,the effect of annular slot electromagnetic stirring on solidification structure of alloy melts was studied.the results of the study found that:unlike Al-5Ti-B refiner,Al-5Ti-B-1RE refiner does not degenerate with the extension of time,and is more refined than Al-5Ti-B refinement.The agent has better refinement effect.When the addition amount is 1.Owt%,the refinement effect is the best;the addition of Sr effectively changes the morphology of the eutectic silicon,and changes from strip to rod-like,spherical,when the amount of Sr is 0.04wt%,the modification effect of eutectic silicon is the best;the annular seam electromagnetic stirring has a great influence on the morphology and size of the solidification structure of the melt.From the aspect of the microstructure,no ring seam type is added.Before the electromagnetic stirring,the primary phase was dendritic.After the ring-stitch electromagnetic stirring,the primary phase was rose-like or polygonal.In terms of tissue size,the tissue is relatively large before stirring without electromagnetic stirring,and the primary phase is further refined after electromagnetic stirring using a circular seam.The large-scale aluminum alloy casting hub with a diameter of more than 20 inches was prepared using the optimized composition and melt treatment process on a low-pressure casting machine.The differences in the organization of the hub parts were reduced,the structure was more dense,and the wheel hub mechanics Performance:tensile strength 388Mpa,yield strength 281MP,elongation of 12.1%,compared to the traditional process of casting wheels,tensile strength increased by 25%,yield strength increased by 24%.