Sand castable Al-Si alloy makes linerless engine blocks

摘要

An aluminum-silicon alloy that provides enough hardness to make linerless engine blocks has reportedly been developed by Mercury Marine, Fond du Lac, Wis. Designated Mercosil (AA B391), the alloy contains 18 to 20 percent silicon. The alloy was developed for lost foam casting, and contains 50 percent more primary silicon than aluminum alloy 390, which results in improved wear resistance. In addition, its solidus temperature is 55 deg C (100 deg F) higher than aluminum alloy 390. However, the temperature difference between the liquidus and solidus is smaller than in 390, resulting in more uniform distribution of primary silicon, and less primary silicon segregation. Because it is free of copper, Mercosil responds to moderate pressure during solidification, which results in lower porosity, said to be 0.01 percent approximately.