Heat Treatment And Impact Failure Analysis Of A356 Aluminum Wheels

For the past few years, the world has been suffered a severe energy crisis. The demand to lighten the cars has increased continuously. Meanwhile, much more requirement of the impact properties has been put forward because of the importance of the safety and stationary. Under such background, the heat treatment and impact properties of the A356 aluminum alloy wheel hub were studied in this paper. The research could provide theoretical guidance for the actual production.The influence of the solid solution treatment process and the aging treatment process on the mechanical properties of the A356 aluminum alloy was mainly studied in this paper. The heat treatment process was optimized through testing the tensile properties, and observing the fracture morphology, the metallurgical microstructures, and the transmission microstructures. The finite element simulation method was used to analyze the weak position on the wheel hub during the 13 ° impact test. The results were proved by the actual impact test. The impact properties, the fracture morphology, the metallurgical microstructures around the fracture, and the tensile properties of the wheel arms of different wheel hubs with different structures were compared. Finally, factors that influencing the impact properties of the aluminum wheel hubs were found out.Results showed that excellent properties of the A356 alloy was obtained after solid solution at 540 °C for 5 h, where the tensile strength was 268 MPa, the yield strength was 150 MPa, and the elongation was 13.7 %. The optimized aging treatment process was holding at 155 °C for 4 h. After that procedure, the tensile strength was 299 MPa, the yield strength was 199 MPa, and the elongation was 17.6 %. The higher strength value and the better elongation could be obtained within relatively short time through two stage aging process. This could be attributed to the G.P. area formed during the first stage because G.P. area could provide favorable condition for the formation of the β``phase which could effectively strengthen the matrix.13 ° impact test results showed that factors influencing the impact properties of the aluminum wheel hub included the structure of the wheel hub, the casting quality, and the microstructure state. The 13 ° impact test properties were weakened by shrinkage porosity produced during casting, bad modification treatment, the eutectic silicon segregation and the needle-shaped iron phase. Thus the impact properties could be improved by improving the quality of the low-pressure casting, using the reasonable modifier, employing the double wheel arm structure and strengthening the wheel arms.