Casting of Aluminum - Fly Ash Composites for Automotive Applications 2003-01-0825

It has been shown that fly ash can be incorporated in aluminum alloy matrix using stir casting and pressure infiltration techniques; additions of fly ash have been shown to decrease the density and coefficient of expansion of aluminum and increase its wear resistance. This paper summarizes the work in progress at University of Wisconsin-Milwaukee and Eck Industries, Inc. on incorporating fly ash in aluminum castings to decrease the cost and weight of selected industrial components. Aluminum alloy A356 - fly ash and 319-fly ash composite ingots and selected parts were successfully cast in sand and permanent molds using conventional foundry techniques from large scale heats (400 pounds). The sand and permanent mold castings including differential carriers, intake manifolds, brake drums and outdoor equipment castings show adequate castability of the melts containing fly ash particles. The results of microstructure analysis and property examination indicate that the strength of casting is significantly influenced by the amount and distribution of fly ash particles in the castings. The room temperature tensile strength of composite castings containing less than 8 vol. % fly ash is similar or slightly lower than that of the base alloy and then decreases with further increase in fly ash contents. The tensile strengths measured at 600°F for the composite castings containing 2 to 12 vol. % fly ash are significantly higher than tensile strengths of the base alloys. Additional work is required to prevent particle agglomeration and adequate mixing at fly ash levels in excess of 10%. This work and prior work on squeeze cast motor mounts and pressure die cast mounting brackets suggest that the aluminum-fly ash alloy may be suitable for selected automotive applications.