The content of alloying elements in this type of alloy is generally more than that of the corresponding wrought aluminum alloy.
According to the difference of main alloying elements, there are four types of cast aluminum alloy.
1) Aluminum-silicon alloy, also called "silicoalumina" or "silicoalumina". It has good casting performance and wear resistance, low thermal expansion coefficient, the most variety in cast aluminum alloy, and the alloy with the largest amount of silicon content is 10%-25%. Sometimes 0.2%-0.6% magnesium silicon-aluminum alloy is widely used in structural parts, such as shells, cylinders, boxes and frames. Sometimes adding an appropriate amount of copper and magnesium can improve the mechanical properties and heat resistance of the alloy. Such alloys are widely used in the manufacture of pistons and other components.
2) Aluminum-copper alloys, alloys containing 4.5%-5.3% copper have the best strengthening effect. Appropriate addition of manganese and titanium can significantly improve room temperature and high temperature strength and casting performance. It is mainly used to make sand castings that bear large dynamic and static loads and have uncomplicated shapes.
3) Aluminum-magnesium alloy, the lowest density (2.55g/cm3), the highest strength (about 355MPa) cast aluminum alloy, containing 12% magnesium, the best strengthening effect. The alloy has good corrosion resistance in the atmosphere and seawater, and has good comprehensive mechanical properties and machinability at room temperature. It can be used for radar bases, aircraft engine casings, propellers, landing gears and other parts, and can also be used as decorative materials.
4) Aluminum-zinc alloys, silicon and magnesium are often added to improve performance, often called "zinc-silica-aluminum". Under casting conditions, the alloy has a quenching effect, that is, "self-quenching". It can be used without heat treatment. After modification and heat treatment, the casting has higher strength. After stabilization, the size is stable, and it is often used to make models, templates and equipment supports, etc.