Applied Fundamental Study On Precision Forging Of Aluminum Alloy

Due to the condition of energy, environment and security over the world become more severe, light weight fabrication is to prove to be an important strategy for sustainable development. The precision plastic forming of light weight aluminum component with high strength become a research hotspot in the field of light weight fabrication. The internal and external conditions during precision forming play an important role in metal flow and microstructure change, which influences the strength of forging. Thus, to find out the influence of technological and structural conditions on forging shape, microstructure evolution and strength, applied fundamental studies were conducted on 2397 and 4032 aluminum alloy and rib-web component used in aerospace and automobile industry.Dynamic recrystallization model of 2397 aluminum alloy considering the effect of initial grain size, strain, strain rate and temperature was established based on the results of isothermal compression experiment, microstructural observation and flow stress analysis. The model enables to predict recrystallized grain size, recrystallization volume fraction and average grain size. The dynamic recrystallization behavior of 2397 aluminum alloy during hot upsetting was simulated by finite element program DEFORM-2D integrated with recrystallization model. Physical experiments also were carried out to verify the accuracy of the model.The metal flow behaviors of closed and open rib-web component during closed hot forging were investigated by numerical simulation and experiment. The grain size distribution was predicted by finite element program DEFORM-3D integrated with dynamic recrystallization model. The influences of technological parameters, such as billet temperature, die temperature and forming velocity, and structural parameters, such as rib width, web height and round radius of between rib and web, on rib filling and forming load were studied. Then, the design criteria of structural parameters were summarized. A new preforming design method was proposed to manufacture those rib-web components which can not be easily formed in one step. The height difference between outer rib and inner rib calculated by slab method was compensated in preforming part based on reverse analysis, which enable to ensure the metal flow center to locate in the web. To predict forming load, a new envelope circle equivalent model was presented, which can be well characterize the feature of metal flow at the end of forming. A new flow control forming technology which consists of depressurized preforming and damping final forming was presented to reduce forming load and improve workability.The effect of temperature and reduction ratio on mechanical properties of 4032 aluminum alloy was studied by isothermal extrusion experiment, tensile test and microstructural analysis. A comprehensive performance parameter combining tensile strength and ductility was adopted, and an empirical relationship model of performance parameter was constructed by regression analysis in terms of temperature and strain.Take hot forging of piston tail as an example, a forming scheme was designed based on the presented flow control forming technology. According to the metal flow features of two-step processes, a U-type preforming part was designed. The presented performance parameter model was integrated into finite element program DEFORM-3D by its subroutine, which was used to predict forming process and property parameter distribution in forging part. From simulation results, it can be found that the property parameter distribution of U-type preforming part was better than that of the V-type performing part, which demonstrated that the U-type is better for manufacturing the piston tail. Meanwhile, the material utilization was 95%.The research results are provide theory and experiment basis for precision forging of aluminum alloy rib-web component, and have important directive significance to production.