Whole Process Design And Optimization Of Lightweight Wheel Hub For Commercial Vehicles Based On Al-Mg-Si-Sc-Zr Alloy

'Made in China 2025' defines the development direction of China's equipment manufacturing.And its requirements for lightweight development of auto parts'advanced forming,energy conservation and environmental protection suggests a redesign of its structure and process.The development of lightweight high-strength new materials is an important research topic in this regard.Against this backdrop,this thesis focuses on the lightweight developmentof key components of commercial vehicles and carries out a whole process design and research on the same starting from the material research and development together with process and structure optimization.A R&D work was designed in light of the deformed aluminum alloy with the target set to prepare an Al-Mg-Si-Sc-Zr alloy with high strength and optimal plasticity.The existence state of Sc/Zr elements in aluminum alloy and their evolution during plastic deformation and heat treatment were also studied.The relationship and impact among the mechanical properties of the alloy and the heat treatment process,forming process and structure of the alloy were discussed.And the research results are as follows:1.The results of the study on the morphology,size and distribution of the primary phase of Al3(Sc,Zr)with a focus on the precipitation of second phase Al3(Sc,Zr)in the deformed state and its influence on the mechanical properties of the alloy showed that the primary Al3(Sc,Zr)particles could be used as the heterogeneous nucleation site of?-Al matrix during solidification to form fine equiaxed crystal structure;and the Al3(Sc,Zr)precipitation phase strongly impeded dislocation movement and grain boundary migration,leading to significant subgrain boundary strengthening and precipitation strengthening effects.2.On the basis of revealing the micro-evolution principles of Al3(Sc,Zr)in the alloy,the alloy composition was adjusted and rollings of different deformation degrees were carried out to study the high temperature aging of the alloy with the purpose of acheiving maximum precipitation of the second phase Al3(Sc,Zr).The study focused on the quantitative improvement of the alloy properties under this process.And the results showed that the precipitation strengthening increases with the increase of deformation,and the cold rolling had a significant promoting effect on the precipitation kinetics of Al-Sc(Zr).An exploration on the suitable low aging temperature and holding time in order to realize the Mg2Si phase precipitation strengthening was carried out in comparison to microstructure and mechanical properties under 160?,180?,and 200?.And the results showed that when the low aging temperature was 200?,the yield strength,tensile strength and the elongation of the alloy were 383.41 MPa,460.35 MPa,and 16.25%respectively.As a result,the Al-Mg-Si-Sc-Zr forging alloy suitable for the wheel hub of commercial vehicles was prepared and the heat treatment process was mastered.3.The forging process of commercial vehicle wheel hub based on the alloy was studied.To control the thermal deformation of the alloy plasticity behavior thermal simulation experiment was carried out to explore the hot deformation behavior during which a processing map was obtained,two best processing areas of Al-Mg-Si-Sc-Zr alloy(deformation temperature 500-540?,strain rate 0.05-1 s-1 and 440-470?,strain rate of 0.01-0.02 s-1)and processing instability areas were identified on the basis of Prasad criterion.Based on these,the forging spinning process was designed and analyzed by numerical simulation,and the appropriate process parameters were determined and optimized based on the stress and strain analysis and feedback process design.4.Dynamic bending fatigue test and radial fatigue test were carried out on the formed hub,and the structural optimization of Al-Mg-Si-Sc-Zr alloy hub was carried out within the range of safety parameters.According to the experimental simulation results,the optimized parameters were selected,and the rim thickness,the flange thickness and the inner diameter of the vent were optimized and as a result,the hub weight was reduced by 5.1%.Then,the influence factor depth and impact of the three design variables on the state variables were analyzed through the sensitivity diagram in the response surface optimization.The material properties were fully utilized by reducing the size of part of the structure,so that the total weight reduction of the wheel hub reached 7%and the safety factor reached 2.4.In this way,the theoretical and experimental references for the lightweight development of commercial vehicles' wheel hub were established from the material research and development and structure and process optimization,and the whole-process lightweight design of wheel hubs of commercial vehicles was realized which shall lay a foundation for the design and manufacturing of development of the new aluminum alloy' application in auto parts industry.