Research On Preparation Of High Strength And Toughness Al-9Si-3.5Cu Cast Aluminum Alloy And Control Arm Casting And Forging Compound Forming

Aluminum-silicon-copper cast aluminum alloys are widely used in aerospace and automotive fields due to their good pouring properties,low density and low price.However,it is difficult for traditional aluminum-silicon-copper alloys to meet the performance requirements of key parts in terms of strength and plasticity.Therefore,this paper independently developed a high-strength Al-Si-Cu series cast aluminum alloy,and prepared a new energy high-strength automobile control arm through a casting and forging composite molding process.The research carried out and the findings of the research are as follows:(1)The effect of multi-element microalloying on the structure and properties of Al-9Si-3.5Cu cast aluminum alloy was studied.The results showed that the Zr-Sr-Ti ternary composite microalloying modified Al-9Si-3.5Cu alloy well,and the alloy eutectic silicon was well granulated,showing vermicular and spherical particles.?(Al)is equiaxed dendritic crystals.Zr-Sr-Ti ternary microalloying better exerts the modification effect of Sr element,and Sr element adsorbs on the growth surface of eutectic silicon to inhibit its growth.The Ti Al3produced by the reaction during the nucleation process acts as an external crystal nucleus to achieve fine-grain strengthening.The tensile strength of the alloy can reach 400.07MPa,the hardness is 139.84HV,and the elongation after fracture is 9.5%.Zr-Sr-Ti-Ce quaternary microalloying has little effect on the size of Al-9Si-3.5Cu alloy?(Al),but it will further affect the size of eutectic silicon and the morphology of the enriched strengthening phase.The hardness of the alloy is increased to 150.96HV,and the tensile strength and elongation after fracture can also reach 391.58MPa and 6.99%.(2)The effects of three multi-stage solid solution processes on the microstructure and properties of Al-9Si-3.5Cu-0.2Zr-0.1Sr-0.16Ti alloy are studied.The results of the study found that the effect of solution treatment on Al-9Si-3.5Cu-0.2Zr-0.1Sr-0.16Ti alloy is mainly divided into the morphology improvement of eutectic silicon and solid solution strengthening.After G1(480?×2h+490?×2h)solution treatment,the eutectic silicon gradually decomposes from coral shape and granulates into worm-like and spherical shapes.These particles are evenly distributed at the grain boundary,and the silicon phase has a good morphology.Through XRD phase analysis,it is found that Al₂Cu is the solid solution strengthening phase of the alloy.After solid solution treatment of G1,it is well soluble in the matrix to play a solid solution strengthening effect.After low-temperature aging,Al₂Cu precipitates again and enhances the properties of the alloy through dispersion strengthening.Continue to increase the solid solution temperature to 510°C,and the dispersed metal compounds in the alloy will aggregate,the crystal grains will gradually coarsen,and even slight over-burning will occur.(3)According to the product size of the control arm,design the mold of the control arm casting billet casting system.Then,guided by the numerical simulation analysis of Anycasting finite element software,the slab production process in the casting and forging composite molding is simulated.According to the casting filling,solidification sequence and entrainment sequence,analyze the rationality of the gating system and whether the porosity and slag inclusion phenomenon occurs in the product molding process;by analyzing the residual melt modulus of the casting,determine the probability and area of shrinkage porosity.Use the same method to determine the influence of different process parameters on the quality of castings.The results showed that the casting speed of 0.5m/s,the casting temperature of 740?,and the mold preheating temperature of 400?are the best casting processes for castings.(4)Design the hot die forging size of the casting billet,and use the numerical simulation analysis of Deform-3D software as a guide to analyze the forming law of the control arm in the die forging process.The results found that:by analyzing the Z-direction load of the upper die,the forging process of the control arm can be divided into the upsetting stage,the filling stage and the knocking stage.Through equivalent strain analysis,it is found that the workpiece has general deformation zone,difficult deformation zone and large deformation zone during die forging process.When the die forging process parameters are 450?for forging temperature,200?for die temperature and 2mm/s for upper die forging speed,the control arm forming stress and strain distribution is reasonable,the metal flow is reasonable during the forming process,and the velocity vector distribution is uniform.The product is well formed and the surface quality is good,which can provide parameters and theoretical basis for actual production.