Silumin is the name that is used in some countries for alloys based on Al–Si system. Silumin is a series of lightweight, high-strength aluminium alloys with silicon content within range of 3–50%. Most of these alloys are casting ones, but also it would be produce by rapid solidification processes and powder metallurgy. Within the Aluminum Association designation system silumins are corresponding to alloys of two system: 3xx.x – Aluminum–silicon alloys are also containing magnesium and/or copper, and 4xx.x – Binary aluminum–silicon alloys. Among the advantages of silumin is its high resistance to corrosion, making it useful in humid environments. The addition of silicon to aluminium also makes it less viscous when liquid, which together with its low cost (both component elements are relatively cheap to extract), makes it a very good casting alloy and a fresher metal. It is also used on 3 phase motors to allow speed regulation. Another use is rifle scope mounts and camera mounts.
High castability, high fluidity, high corrosion resistance, high ductility, low specific gravity, high machinability
Used for large castings, which are to operate under heavy load conditions
Under the category of non-heat-treatable alloys but can be modified by the addition of Mg & Cu, which enables it to be heat treated, e.g. AΠ4 alloys
Strengthened by solution treatment, e.g. adding 0.01% Na (in form NaF & NaCl) to the melt just before casting
Disadvantage is the presence of porosity in the cast (forms foams), which can be avoided by casting under pressure in autoclaves