High Performance Aluminum Casting Alloys for Engine Applications

In the early 1980's, some promising research and development efforts focused on powder metallurgy revealed that aluminum alloys containing 4 wt% cerium exhibit high temperature mechanical properties exceeding those of the best commercial aluminum casting alloys currently in production. Cerium oxide is an abundant rare earth oxide that is often discarded during the refining of more valuable rare earths such as Nd and Dy. Therefore, the economics are compelling for cerium as an alloy additive. In this paper, we report select results obtained during an investigation of the castability of aluminum-cerium alloys and determine compositional modifications that may be required to ensure the compatibility of the alloy with near net shape casting methods such as advanced sand casting, die casting, permanent mold casting and squeeze casting. Al-Ce alloys were cast in binary composition of 6-16 wt% Ce. Commercially pure aluminum ingots were melted and held at approximately 785°C. Ternary and quaternary alloys with Si and Mg additions were also investigated. Test bars were cast to establish mechanical properties and step plates and hot tear molds were used to determine sensitivity to solidification conditions and hot tearing sensitivity respectively. Finally, air cooled engine cylinder heads were cast in sand molds to get a sense of castability in complicated shape castings.