Zinc is a natural element found as a component of the earth’s crust. With deposits spread widely throughout the world, zinc ores are extracted in more than 50 countries. Added as a dietary supplement in vitamins, facial creams and sun blockers, zinc is an indispensable part of our daily lives.
The most widely used zinc alloy is commonly called No. 3. Its excellent all-around physical and mechanical properties, superb cast-ability, and long-term dimensional stability have made it the choice for about 85% of U.S. die-castings. In most design applications using a zinc alloy, No. 3 will do the job. In general, only after casting design improvements have been evaluated and found inadequate should another alloy be considered.
The addition of about l% copper to the No. 3 alloy provides increased tensile strength (about 15%) and higher hardness at the expense of elongation and impact strength. No. 5 alloy is widely used in Europe, but accounts for less than 10% of U.S. consumption.
Actually, a predecessor of the universal No. 3 alloy, No. 2 offers the highest strength and hardness available in a conventional zinc alloy. It is about 25% stronger as cast than No. 3 and 10% stronger than No. 5 with higher hardness than both.
The principle disadvantages of this interesting alloy are its very low impact strength and elongation after aging (especially at higher temperatures) and a slight dimensional instability with aging.
The third most popular alloy is a high purity, low magnesium alloy called No. 7. This alloy has improved fluidity (because of the lower magnesium content) allowing it to be cast at lower temperatures for better as-cast surface finish and higher production rates. Most No. 7 alloy is used in decorative hardware applications. Since it possesses slightly more ductility than other zinc alloys, No. 7 is also used where castings require severe deformation in assembly operations.
Offers best plating and finishing characteristics with improved strength, hardness and creep properties compared to the other conventional zinc ZAMAK die casting alloys. Major application area is usually for die casting where improved properties over ZAMAK’s are required, particularly performance at elevated temperatures.
This is the most recent development in commercially available zinc die casting alloys. Research has shown EZAC™ to be the most creep resistant of all the zinc die casting alloys with over an order of magnitude improvement over ZAMAK 5 and ZA-8. This is also a very strong alloy with a yield strength (57 ksi) and hardness (102-134 brinell) comparable to ZA-27.
Due to its low melting temperature, EZAC™ can be cast in a hot chamber die casting machine and does not exhibit the same wear and tear as shown with ACuZinc®5.
Zinc die casting alloys are versatile engineering materials. As a result, no other alloy system provides the combination of strength, performance, and economical castability. Listed are zinc alloy attributes which can potentially reduce component costs and/or improve you design performance. This information will serve as a guide to help designers understand the capabilities of zinc die cast alloys for product applications.
See our zinc alloy property guides below for additional information.