Phenomenological studies on solidification and casting of aluminum and magnesium alloys

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Weight reduction, enhanced fuel efficiency (2025 CAFE: 65.4 MPG), energy conservation, reduced carbon emissions and recycling have become cornerstones for a prosperous global economy and high quality of life. Light alloys of aluminum (density: 2.70 g/cm3) and magnesium (density: 1.74 g/cm3) hold much hope, and provide scope for the development of novel manufacturing processes for the automotive sector. However, there are still some challenges impeding the increased use of these alloys, because they are particularly prone to forming casting defects (e.g., inclusions, porosity, hot tearing, misruns, distortion) during solidification. There is also a need to improve the high temperature performance of aluminum alloys used in engine systems (e.g., engine blocks, cylinder heads) with improved operating efficiency. For magnesium alloys, specific needs include the development of new grain refiners for enhanced strength and castability. This research program seeks to build upon extensive research experience, knowledge and success in castability and characterization of aluminum and magnesium alloys. It envisages a deeper understanding of solidification mechanisms, with a view to reducing the formation of casting defects and improving the mechanical properties of aluminum and magnesium alloys. A new methodology, based on neutron diffraction analysis, will be used to characterize the formation of defects in aluminum and magnesium alloys, specifically for relating the microstructure, strain/stress and hot tear formation. In-situ and ex-situ neutron diffraction will be used for dynamic monitoring of solid fractions of phases and for residual strain/stress mapping. Commercial software will be utilized for modeling heat transfer, hot spots, heat flow, fluid flow and hot tearing in conjunction with neutron analyses and microstructural characterization. The fundamental knowledge gained from both the modeling and the laboratory experiments will be used to explain and predict the formation of casting defects with a view to transferring the knowledge on an industrial scale for foundry and in-service automotive applications. For aluminum alloys, a systematic study relating solidification conditions, heat treatment procedures, mechanical properties and residual strain/stress will be carried out, with a view to eliminating distortions in castings. Novel magnesium grain refiners will be synthesized with appropriate ball milling and sintering for the development of high performance castings. The program will reinforce and enhance an excellent track record of HQP training. The impact of this research will be felt in the 3Es: Energy, environment and economy. Elimination of fuel leakage, increased operating efficiency and extension to new technologies (e.g. linerless engine blocks) will result in increased lightweighting, directly impacting conservation of energy and reducing greenhouse gas emissions. Overall, these advances will reduce recalls (via elimination of distortion) and significantly decreased scrap rate of castings (thru elimination of hot tearing) ensuring enhanced profitability for the Canadian automotive industry, contributing to the revival of the auto economy. As a consequence, they will significantly help in developing standards, policies and overall vision for automobile weights and related emission levels.