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.