The Elements of Zinc Aluminum Alloys in Die Casting

The zinc aluminum alloys are denoted by the letters “ZA” and the numbers following the hyphen denote the nominal aluminum content on approximate. There are three main ZA alloys, namely ZA-8, ZA-12, and ZA-27.

The ZA-8 alloy has nominal aluminum content of above 8.4 percent and copper content of 1 percent. ZA-8 alloys have the lowest melting point of the lot and highest density of the three types of ZA alloys. The ZA-8 alloy has high tensile strength and creep strength, and can be chrome plated using similar process used for standard zinc alloys. Die casters use the hot chamber die casting process to cast ZA-8 alloy.

The ZA-8 alloy is considered as superior to secondary aluminum alloys used in die casting aluminum. The ZA-12 alloy, on the other hand, has nominal aluminum content of above 11 percent and copper content of 1 percent. ZA-12 alloys are used in applications such as bearings, permanent mold, and so on.

The ZA-27 alloy has nominal aluminum content of above 27 percent and copper content of 2.2 percent. The ZA-27 alloy has the highest aluminum content and hence the highest tensile strength, highest melting point, and lowest density of the three ZA alloys.

ZA-27 alloys are not usually chrome plated. Moreover, since aluminum content and the casting temperature increase, ZA alloys become more aggressive to iron and steel alloys. However, using ZA alloys reduce the die life and somewhat increase the maintenance cost of the component.

Note that the aluminum and copper content on ZA alloys offer several advantages over standard types of zinc alloys such as high tensile strength, corrosion resistance, creep resistance, and lower densities. During the late 1950’s, ZA alloys were used in gravity casting. However, research and development have lead to a stage wherein even the foundry engineers use the ZA alloys in manufacturing of components.

The use of pure aluminum is generally rare because of the cost of extraction, say prominent die casters in the ancillary segment. So when die casting aluminum, the alloy is derived by melting and mixing raw aluminum with other alloys such as iron, magnesium, and copper.