Automotive design engineers are looking for higher performance engines. Whether this translates into more horsepower on the racing circuit, or improved fuel economy in passenger cars, the end result is increased stress and higher temperatures in the engine. Especially problematic are conditions in the dome area of cylinder heads. A number of high temperature alloys have been proposed over the years, and these are briefly reviewed. Unfortunately, the alloys offering best mechanical properties have relatively poor castability. Computer-based calculations of phase relations in the Al-Si-Cu-Mg system, combined with the use of aluminide forming elements (Ti, V and Zr) have resulted in a new high strength alloy having excellent castability. It has recently been registered as AA 351. Some of the heads and blocks made with the material are described, together with results in the foundry and on the race track.
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