Modeling of Microstructure and Mechanical Properties of Aluminum Alloys during the Casting and Heat Treatment Process

In the production of aluminum castings, alloy composition, metallurgy, and local solidification conditions determine the distribution of microstructure and defects. The local distributions of microstructure and defects have a defining impact on the mechanical properties. This paper will present an overview of new options to simulate the local microstructure in casting processes and throughout the entire heat treatment. Based on the calculated microstructure at the end of the complete process chain, the mechanical properties will be predicted. This local information can be utilized already in the casting design process as input parameters for the simulation of further process steps, i.e. lifetime prediction. They can also be used to optimize the casting and heat treatment process itself, to achieve the desired mechanical properties within economical boundaries. Thermodynamic phase diagrams and models for the growth kinetic of metallic phases are the basis for the calculation of microstructures and mechanical properties. The creation of microporosity is described by a model, which considers the interdendritic feeding behavior, as well as the precipitation of hydrogen. The as-cast microstructure, especially the volume fraction of Mg2Si and Al2Cu phases, provides the input parameters for modeling the diffusion and precipitation of phases during the heat treatment. The mechanical properties of the part at the end of the heat treatment process are derived from the size and distribution of precipitating phases, as well as from the Mg/Cu-content of the matrix. The utilization of process simulation, as well as a comparison of measured data, is shown using the example of a cylinder head, discussing the options to use these results during the part development and process optimization phases.