Squeeze Casting of Wrought Mg Alloys for Lightweight Structural Automotive Components

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The average Mg content in 2015 North America built cars was 5 kg, compared with an increase from 3 kg per vehicle in 2000. By 2025, the usage of Mg is expected to triple to about 15 kg per vehicle due to its lightweight property. The current Mg automotive components are mainly manufactured by conventional high pressure die casting processes (C-HPDC) with the conventional cast Mg alloys. The mechanical properties of C-HPDC alloys are affected by casting defects, which reduce the strength and ductility. C-HPDC Mg components are prone to high levels of porosity because of severe turbulence of the molten alloy that enters the die cavity. There is a major limitation on the use of C-HPDC Mg castings in critical areas of the vehicle including chassis, body frame and suspension due to the inadequate mechanical properties of the conventional cast Mg alloys. The structural components in the critical areas require high strength, high ductility and improved corrosion resistance, and are capable of functioning in cyclic loading and corrosive environment. To expand Mg applications into structural and safety-critical parts of both gasoline or diesel-powered vehicles (GDVs) or battery-powered electric vehicles (BEVs), such as knuckles, control arms, subframe, unibody, door frame and seat belt brackets, which experience a high cyclic mechanical loading during service, the development of cost-effective manufacturing processes is essential to produce lightweight high-integrity structural automotive components. Low-cost wrought Mg alloys possess sufficient ductility and strengths to ensure that lightweight high-integrity structural applications have consistent excellent plasticity and high strengths. The long term objective of this proposal is to exploit the unique engineering performance and qualities of inexpensive wrought Mg alloys with squeeze casting (SC) for automotive applications, particularly high-integrity structural components in GDVs or BEVs. The proposed research program will employ a systematic design approach guided by comprehensive processing-microstructure-property relationships of the low-cost SC wrought Mg alloys (LSCWMAs) with high plasticity and strengths. The short term objectives in the next five years are: (I) development of squeeze casting processes for low-cost wrought Mg alloys and (II) evaluation and characterization as well as optimization of the LSCWMAs. This new technology will put Canada at the leading edge in emerging markets for high-integrity lightweight structural applications. The OEMs present in Canada (Ford, Toyota, GM, Honda and Chrysler) need high-integrity lightweight structural applications for their GDVs and BEVs. Ontario hosts the world's largest Mg die casting company, Meridian. The development of new Mg processes for potential advanced products will lead to an increase in Mg-based castings made in Canada as well as an expansion of world-wide use of Canadian value-added lightweight products.