High-Performance Aluminum Castings Containing Rare Earth Elements

Abstract

Cerium(IV) oxide (CeO₂) is one of the predominate oxides produced in rare earth mining. Much of it is discarded after separation from the higher atomic number rare earth oxides. A beneficial use of cerium (Ce) is being sought to reduce the cost of producing the more desirable rare earth elements.

Aluminum (Al) alloys containing small amounts of Ce have been investigated to improve their grain refining, casting characteristics and mechanical properties. Cerium containing mischmetal has also been studied in some depth. These additions were usually made at levels of 1 wt% or less and appreciable material property improvement was not evident. Recent work has shown that additions between 4 wt% and the approximate eutectic composition of 10 wt% improve the high-temperature performance of Al alloys.

Corrosion performance of Al alloys can also be improved through the addition of Ce. Traditional Al alloying elements such as magnesium (Mg) and silicon (Si) can be used to control casting characteristics and thermal and physical properties.

The result of using Ce as an addition to Al alloys in multiple manufacturing methods such as additive manufacturing, extrusion and casting is explored in this chapter. Significant strengthening and improved mechanical property retention at elevated temperature has been demonstrated, and in some compositions, complete recovery of room temperature mechanical properties resulted after exposure to elevated temperatures as high as 500 °C for 1000 h.