Alusil

Alusil as a hypereutectic aluminium-silicon alloy (Al17Si4CuMg or A390) contains approximately 78% aluminium and 17% silicon. This alloy was created in 1927 by Schweizer & Fehrenbach of Baden-Baden Germany and further developed by Kolbenschmidt.

The Alusil aluminium alloy is commonly used to make linerless aluminium alloy engine blocks. Alusil, when etched, will expose a very hard silicon precipitate. The silicon surface is porous enough to hold oil, and is an excellent bearing surface. BMW switched from Nikasil-coated cylinder walls to Alusil in 1996 to eliminate the corrosion problems caused through the use of petrol/gasoline containing sulfur.

Engines using Alusil include:

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