Microstructure based analysis and predictive modeling of cast Al7Si1.5Cu0.4Mg alloy mechanical properties

The heterogeneity of microstructure leads to non-uniform distribution of mechanical properties, which is also related to strength and reliability degradation of components. Taking diesel engine cylinder heads as an example, this study investigated the relationship between microstructures and tensile mechanical properties of cast Al7Si1.5Cu0.4Mg alloy with different temperatures, including secondary dendrite arm spacing (SDAS), grain size, eutectic silicon morphology. The results indicate that the mechanical properties of cast Al7Si1.5Cu0.4Mg alloy have a strong correlation with the microstructures. Based on the linear regression analysis method, several predictive models were established to quantify the tensile mechanical properties of cast Al7Si1.5Cu0.4Mg alloy with different microstructures. The Hall-Petch model was used to capture the relation between microstructure parameters and yield strength, and a linear relationship model was employed between the hardness and yield strength. The prediction model of ultimate tensile strength was proposed based on the relationship of microstructure and hardness. In addition, considering the error limit of the Hall-Petch relationship, the upper threshold of grain size and SDAS is calibrated. By considering the influence of the material's plastic deformation ability and the material strength on fatigue performance, a novel Tensile-Fatigue Bridge Model was proposed. The model provides a reference for the mechanical properties prediction work of thin-walled small parts and also contributes to the strength evaluation of components with non-uniform microstructures.