Study on the High-Cycle Fatigue and Fatigue Crack Growth Behavior of Al-Si-Mg Alloy: Pore Size and Stress Ratio Effects

Defects are inevitable products during the manufacturing process of cast aluminum alloys, which have a significant impact on the service performance of engineering components under complex loadings. However, the effects of casting defects and stress ratio on the fatigue properties of Al-Si-Mg alloys are still not fully understood. In this study, the effects of pores defects and stress ratio on high-cycle fatigue and fatigue crack growth behavior of Al-Si-Mg alloy were systematically investigated. The experimental results show that the high-cycle fatigue properties of Al-Si-Mg alloy exhibit high dispersion, while low dispersion displayed for the fatigue crack growth rate. Based on the mechanical parameters and fracture characteristics, it is elucidated that the pore defect has a greater effect on crack initiation than crack growth mechanism in Al-Si-Mg alloy. According to the data validation, Goodman's model could well explain the stress ratio effect on the fatigue strength of Al-Si-Mg alloy than Walker's and SWT's models. Additionally, Kujawski's model, Huang's model, Zhan's model, and Li's model all could predict the fatigue crack growth rate of Al-Si-Mg alloy for different stress ratios. There is no material-dependent parameter in Li's model, which might be an advantage in predicting fatigue crack growth rate of metallic materials.