Effect of Pore Size on the High Cycle Fatigue Property of Al-Si-Mg Alloy for High Speed Train Gearbox Housing

Casting defects are the important factors in casting aluminum alloy, which would significantly reduce the fatigue life of engineering components. In this study, the quantitative relationship between the pore size and high cycle fatigue property of Al-Si-Mg alloy for high-speed train gearbox housing was systematically studied. The projected areas of pores within the fracture zone for all failed specimens were systematically measured. The equivalent diameter of most pore defects is less than 400 μm, and the median equivalent diameter of the pore defects is 280 μm. The effect of pore size on the fatigue life of Al-Si-Mg alloy is expressed by the improved Shiozama model, which can explain its fatigue life dispersion. Additionally, the critical defect size of Al-Si-Mg alloy calculated by the standard KT diagram is 276 μm. The results would provide a theoretical basis for the manufacturing process and evaluation standards of high-speed train gearbox housing.