AlSiMg

AlSiMg is a family of aluminum casting alloys in which silicon and magnesium are the principal alloying elements. The base metal is aluminum, and the combination of silicon for improved castability and magnesium for precipitation-hardening provides a balance of good finish, strength, and wear resistance. These alloys are widely used for gravity casting and low- to medium-pressure die casting.

Composition and grades vary by standard and supplier. Silicon is typically in the mid-single digits to around ten percent, while magnesium ranges from a small amount up to about one to a few percent in some grades. Other elements may be present as minor additions or impurities. The exact composition defines the alloy’s heat-treatability, strength, and corrosion behavior. In many AlSiMg alloys, strengthening occurs through heat treatment, with magnesium contributing to the formation of strengthening precipitates such as Mg2Si.

Properties and processing. AlSiMg alloys exhibit good fluidity in molten state, low shrinkage, and good surface finish, making them suitable for intricate castings. They respond to heat treatment, improving strength and hardness, while retaining relatively good ductility. They also offer respectable corrosion resistance and decent machinability after proper aging. Typical applications include automotive engine components, housings, pump casings, and other cast parts where a combination of castability and strength is valuable.

Standards and equivalents. The designation AlSiMg refers to the alloy class rather than a single fixed composition. Specific grades (for example, those indicating approximate silicon content) are defined in national and international standards and by alloy suppliers. Recycling and compatibility with other aluminum alloys are common characteristics of this family.