Development of microstructural solidification simulation code for light alloys

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The ultimate goal of the candidate’s research is the development of virtual simulation tools for high temperature industrial metallurgical processes based on thermodynamic databases and kinetic models. In order to achieve this goal, the previous Discovery Grant (DG) focused on the development of thermodynamic database for pyrometallurgy and alloys. Many thermodynamic databases have been developed as the results of DG and also other research grants over the last five years. In this DG, the candidate would like to develop a kinetic solidification model to utilize such thermodynamic database for real casting process. Most of light alloy products are produced through the casting process. Therefore, the as-cast microstructure is one of the determining factors that control the mechanical properties. However, the evolution of as-cast microstructures with casting parameters is still not well investigated. In the casting industry, computational fluid dynamics and heat flux simulations performed by commercial software packages like FLUENT and MAGMA are mostly used to understand the filling behavior in very complex casting molds. Unfortunately, such software cannot provide accurate microstructural information about the casting conditions. On the other hand, phase field modeling was pursued to simulate the development of as-cast microstructures in 2-D and 3-D views, but the calculation is too slow to be directly applied to the practical casting simulation of multicomponent alloys. So, a simple but practical kinetic microstructure simulation model is needed for computational materials design in casting. In the present research program, a versatile 1-D microstructural solidification model with a user interface will be developed to cover a wide range of commercial Mg and Al alloys under a wide range of casting conditions. No such dedicated solidification simulation tool is currently available for Mg and Al alloys. In the past years, the candidate’s research group has carried out fundamental and comprehensive casting experiments to understand the evolution of the as-cast microstructure of Mg-Al-Zn alloys and Mg single crystal diffusion couple experiments to measure the diffusivity in Mg-Al and Mg-Zn systems. All key solidification theories to explain the microstructure development during solidification will be taken into account in the 1-D microstructural solidification model. Moreover, the thermodynamic database, which can calculate solidus, liquidus and equilibrium secondary phases, will be dynamically linked to the kinetic solidification model. This solidification model will calculate, within a short time (less than 10 min), all the important solidification microstructural features such as the primary and secondary dendrite spacing, the solute segregation in dendrite, and the amount of secondary precipitates according to casting parameters at a given alloy. In order to validate the model calculations, well-controlled casting experiments will be performed for Mg and Al alloys. In addition, diffusion couple experiments will be carried out to determine the diffusivities of various solutes in Mg alloys.The kinetic model and experiment can give deep scientific understanding of the solidification process of Mg and Al alloys. The kinetic solidification model can be eventually linked directly or indirectly to CFD simulation tools to predict the as-cast microstructure. Many casting companies in Canada including Alcan, Novelis and Sapa and final materials users like GM-Canada will be able to use the developed knowledge in their optimization of casting processes and the development of new materials. 4 Ph.D. students and 0.5 PDF will be trained over 5 years of the proposed research program.