Light Alloys, Alloy Designations
Index
Light alloys are based on low density metals such as aluminum and magnesium. 

For the aluminum system the following designations are used.
1xxx alloys are essentially pure aluminum 
2xxx denotes a two phase alloy with Cu
3xxx a substitutional alloy with Mn
4xxx a two phase Si alloy
5xxx a substitutional alloy with Mg
6xxx a two phase system with both Si and Mg
7xxx a two phase alloy with Zn. 

Magnesium has a lower density (1.74 Mg.m-3) than aluminum (2.7 Mg. m-3) and its alloys are useful for aerospace applications. Aluminum, manganese and zinc are the major alloying elements. The alloying elements are designated by a letter code: A = Al, K = Zr, M = Mn, E = rare earths, Q = Ag, S = Si, 
H = Th, Z = Zn, and T = Sn.