ALSI

AlSi, shorthand for aluminum-silicon, denotes a family of aluminum alloys in which silicon is the main alloying element. These alloys are widely used as casting materials because of their excellent castability, low shrinkage, and good wear resistance. Silumin is a common industry name for Al-Si alloys.

Silicon content typically ranges from 4 to 20 percent by weight. The eutectic composition is about 12.6 percent Si. Microstructure comprises an aluminum-rich matrix with silicon-rich particles. Hypoeutectic alloys have primary aluminum dendrites with an Al-Si eutectic, while hypereutectic alloys contain primary silicon crystals.

Properties include high fluidity, low shrinkage, and good wear resistance, aiding complex shapes and good surface finish. Silicon reduces thermal expansion but increases brittleness; higher Si lowers ductility. Many common die-cast variants are not strongly age-hardened, though some Al-Si-Cu-Mg alloys can be heat treated to gain strength.

Processing and applications: Most are produced by melting aluminum and adding silicon, often with small amounts of magnesium, copper, or manganese to tailor properties. Die casting is widely used for automotive engine blocks, cylinder heads, pump housings, and other lightweight components. In additive manufacturing, alloys such as AlSi10Mg are used for powder bed fusion.

See also: Silumin; Al-Si alloy family.