Zamak 3 is the most commonly used alloy in zinc die casting, making it the “standard” by which other zinc alloys are rated. Over 70% of all North American zinc die castings are in Zamak 3 due to its superb castability, long-term dimensional stability and attractive balance of desirable physical and mechanical properties. Zamak 3’s finishing characteristics are excellent. It has high performance with all types of finishing including plating, painting and chromate treatments.
Zamak 5 alloy castings are considerably stronger than Zamak 3, but this gain in strength is coupled with a reduction in flexibility. This can be a problem if parts require secondary bending, swaging, crimping or riveting operations. This reduction in ductility is due to a 1% addition of copper. Zamak 5 has excellent castability traits and better creep performance than Zamak 3. Because Zamak 5 is less available than Zamak 3, material specifiers encourage strengthening design modifications in lieu of acquiring Zamak 5. However, when extra tensile performance is necessary, Zamak 5 alloy castings are recommended. It is readily plated, finished and machined. It’s considered comparable to Zamak 3 alloy.
Zamak 7 is almost the same as Zamak 3 except for a decrease in the magnesium content in order to increase fluidity. Zamak 7 has lower levels of impurities and a small amount of nickel which helps to avoid problems with inter-granular corrosion. It has slightly better ductility than Zamak 3 while other characteristics remain constant. These traits make Zamak 7 a popular choice for unique cases where the die caster needs thin walls and an exceptional finish surface.
*It’s important to note that metal and die temperatures have a bigger effect on a finished product than the alloy itself. Paying close attention to control of the die casting process parameters is critical in achieving consistent quality.
Of the ZAMAK family, Zamak 2 (AKA Kirksite) has the highest strength and hardness of any of the Zamak alloys. It is the only ZAMAK alloy used in gravity casting, mainly for metal forming dies or plastic injection tools. Despite its strength advantages, Zamak 2 has high copper content (3%) which causes property changes upon long term aging. Changes may include minor dimensional growth, decreased elongation and a reduction in impact performance (making it more comparable to aluminum alloys). Even though Zamak 2 exhibits excellent castability, it has only gotten limited use by die casters in North America. Nonetheless, there are some traits of Zamak 2 that may be attractive to design engineers; it has higher creep performance than the other ZAMAKs and Zamak 2 sustains better strength and hardness levels after long term aging. Early investigations are suggesting that Zamak 2 may be a useful bearing material which could eliminate bushings and wear inserts in die casting designs.
The market for ZA-8 is growing rapidly. This alloy can be used in gravity casting as well as for pressure die casting. Using ZA-8 in hot chamber die casting results in improved strength, hardness and creep properties over the other ZAMAK alloys (except Zamak 2, which has very similar performance.) Like the ZAMAK alloys, ZA-8 is easily plated and finished using customary processes. Because of its exceptional strength, hot chamber castability and creep properties, ZA-8 is often the die casting choice when the performance of Zamak 3 or Zamak 5 are questioned.
EZAC is a brand new high strength, creep resistant, hot chamber zinc based die casting alloy. It’s an improvement over the other ZAMAK alloys because of its creep resistance, tensile strength, hardness, and high temp tensile properties.
HF stands for High Fluidity, which is exactly what HF was designed for. This new alloy, developed in the Department of Energy Cast Metals Consortium, has displayed improved fluidity in lab tests. It has enhanced cavity fill characteristics and has higher tensile strength and lower elongation than ZAMAK 7.