Zinc-aluminium (ZA)
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...
s are alloys whose main constituents are
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
and
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
. Other alloying elements include
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
and
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
. This type of alloy was originally developed for
gravity casting. Noranda, New Jersey Zinc Co. Ltd., St. Joe Mineral Co. and the
International Lead Zinc Research Organization (ILZRO) were the main companies that pioneered the ZA alloys between the 1950s and the 1970s. They were designed to compete with
bronze
Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids suc ...
,
cast iron
Cast iron is a class of iron– carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuri ...
and aluminium using
sand
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...
and
permanent mold casting methods. Distinguishing features of ZA alloys include high as-cast strength, excellent bearing properties, as well as low energy requirements (for melting).
ZA alloys make good
bearings because their final composition includes hard
eutectic zinc-aluminium-copper particles embedded in a softer zinc-aluminium matrix. The hard particles provide a low-friction bearing surface, while the softer material wears back to provide space for lubricant to flow, similar to
Babbitt metal
Babbitt metal or bearing metal is any of several alloys used for the bearing surface in a plain bearing.
The original Babbitt alloy was invented in 1839 by Isaac Babbitt in Taunton, Massachusetts, United States. He disclosed one of his alloy rec ...
.
The numbers associated with the name represent the amount of aluminium in the alloy (i.e. ZA8 has 8% aluminium).
See also
*
ZAMAK
*
Zincalume
References
{{reflist
External links
Article on ZA12 and the Permanent Graphite Mold ProcessVendor page of material description
Zinc alloys
Aluminium alloys