| As the lightest commercialized metallic material for structural applications,Magnesium alloys are the ideal materials for weight saving, possessing very important and valuable technology enormous utility.Due to their nature of high-speed motion and rotation, weight reduction of the wheels is the most efficient way to reduce the oil consumption, to improve the accelerating and braking performance, to enhance the riding comfort of a road vehicle. Naturally, use of light weight materials on the wheels is the most straight-forward and efficient way to achieve the object. Mg alloys have different mechanical and processing properties in comparison with most widely used steel and aluminum alloys. Consequently, Mg alloys cannot be directly used on the commercial wheels before the structure of the wheels is redesigned in accordance with the service condition and compliant to the processing characteristics of the materials in order to ensure the performance and safety. Considering this characteristics of magnesium alloys develop new forming process.To promote a scientific use of Mg alloys on wheels of road vehicles, the present study was devoted to numerical analyses of stress and strain distributions in a Huatai wheel under identical service condition, structural redesign to reduce the service fatigue stress. Then, mass and heat transfer during die-filling, temperature distribution and solidification, and their effects on the formation of the processing defects during the squeeze casting were analyzed with commercial software to optimize the quality of Mg-alloy wheels manufactured. The main results were highlighted as follows:1. A single piece structure was used for Huatai Mg wheel to replace the previous two halves structure, in order to simplify the manufacturing process, reduce the making of Jig and Fixture Tooling, save cost of labor, energy, and materials, and so on.2. Finite element analysis followed by structural redesign of the Huatai wheel, were conducted with consideration of service centrifugal force, rotating wheel peripheral alternating stress, alternating displacement, the impact of modal, etc...3. Due to the lowered elastic modulus of Mg alloy, the replacement of the original A356 Al alloy with AM60 Mg alloy, the service stress distribution in Huatai wheel becomes more uniform, the peak value of the concentrated stress was reduced from 33.14MPa to 26.14MPa, down 21.12%. The stress distribution in the wheel becomes more uniform and stress variation during a service cycle reduced accordingly. 4. With the optimized squeeze casting parameters of 680℃pouring temperature, 0.3m/s injection speed, 240℃mold preheating temperature and 80MPa holding pressure. The die filling is stable and uniform. The temperature distribution post die-filling is uniform. The solidification process is sequential and stable as expected. The solidification shrinkage voids mainly concentrate in the gating system, which is design to be removed during following-up machining.It can summarized that the replacement of original Al alloy with Mg alloy can not only save the weight by a factor of 27%, but also uniform the service stress distribution, which is important to prevent service fatigue failure of the wheel. The use of the new squeeze casting, the casting cycle is reduced to 120s, and the utilization ratio of the poured melt is above 60%, which is much advantageous in comparison with traditional squeeze casting process. |
