Rapidly increasing fuel prices and demand for low emission vehicles are driving consumers away from large trucks and sport utility vehicles to more efficient cars.
Rapidly increasing fuel prices and demand for low emission vehicles are driving consumers away from large trucks and sport utility vehicles to more efficient cars. Their preferences and proposed US Corporate Average Fuel Economy (CAFE) regulations calling for 34.1 mpg by 2016 and 56.2 mpg by 2025 are motivating North American car companies to re-examine the use of lightweight materials such as aluminum, in their vehicles.
By 2020, average aluminum content is projected to rise to nearly 182 kilograms, up from about 148 kilograms in 2009, as automakers make lighter engine blocks, hoods and other components. As a result, research is focusing on the development of process models for aluminum manufacturing.
The properties of metal products depend on the microstructure of the material, which in turn is a complex function of composition, grain size and orientation, distribution of phases and precipitates and the presence of strain.
A current project involving Nemak Canada, the Natural Resources Canada CANMET Materials Technology Laboratory, the National Research Council Canadian Neutron Beam Centre (CNBC) and the AUTO21 Network is furthering the improved performance of aluminum engine blocks using process models.
Nemak, a Windsor, Ont. manufacturer of aluminium automotive components, uses a novel precision sand casting operation, head deck gated, with integral crank chill, to make engine blocks from cast aluminum alloys. This new technology better controls microstructure and faster cooling rates to produce significantly higher-strength materials. Understanding the material behavior during the casting operation and in-service performance is key. The stability of the microstructure during in-service is especially critical because a precipitation reaction can cause dimensional changes in the product.
Precision sand casting involves a resin-bonded sand that forms a mould that shapes the contours of the engine component. The sand is cured in a solid exterior mould and molten metal is poured into it using a low pressure and electromagnetic pump. This process allows for the use of cast-in-place iron liners in engine blocks and pressurized filling, producing a high degree of dimensional accuracy plus cooling rates that are faster than traditional sand casting technology.
The research has developed and validated new models and process monitoring technologies that ensure more repeatable casting results and better performance in-service. This will help manufacturing engineers better understand the properties of cast materials and the control of casting processes.
Dr. Mary Wells is a researcher for the AUTO21 Network of Centres of Excellence and a professor at the University of Waterloo. Visit www.auto21.ca.