Impact Failure Analysis Of A356 Aluminum Wheels

In order to achieve the goals of lowering energy consumption,lowering pollutant emission and increasing recycled materials in industrial production,the demand for lightweight automobile has increased continuously.Automotive wheel weight loss is the main target for the lightweight automobile.Under this background,A356 aluminium alloy wheels were studied in this paper to investigate the impact properties of aluminum wheels.A detailed analysis of the relationship between aluminum wheels and the microstructures,and the influencing factors of impact properties of aluminum alloy wheels has been taken,providing a theoretical guidance for the actual production of aluminum wheels.13° impact tests on integrated wheels and instrumented impact strength tests on KV sub-size Charpy samples drawn from A356 aluminium alloy wheels have been carried out.The wheels were produced by a low-pressure die casting with different heat treatments.The wheels show thermal treatment with as-cast condition and T6 heat treatment condition.The main factors affecting the impact properties of the wheels were found out by comparing the mechanical properties,fracture morphology,microstructure,porosity and other characteristics of different regions of the two different treatment wheels.Results showed that the impact property in 13° impact tests and the impact energy values in the instrumented impact strength tests are lower in the as-cast microstructure than in the T6 heat-treated one.A finer microstructure and smaller secondary dendrite arm spacing(SDAS)always corresponds to higher impact strength.While a direct correlation between the resistance to crack propagation values(Wp)and SDAS exists.Casting defects,revealed by means of X-ray and density measurements techniques,become critical when concentrated around the V-notch,where they reduce the impact energy of the wheels.Casting defects affect the impact properties has far exceeded the influence of microstructure on impact properties.The resistance to crack propagation values(Wp)are in the range of 65 – 75% of the total absorbed energy and the highest values are shown by the as-cast microstructure in the instrumented impact strength tests.The stability of crack growth of as-cast specimen is better than that of heat treated specimens.The fracture profile and surface of Charpy specimens have been investigated revealing how the crack crosses the interdendritic eutectic region where a significant fraction of cracked eutectic silicon and intermetallic particles is found.The fracture mode is the mix mode of cleavage fracture and ductile fracture.