Comparison of Zinc Die Casting Properties

Tensile Strength

Zinc alloys deliver the highest tensile strength among the most widely used non-ferrous alloys and match or exceed that of most cast irons. Two zinc die casting alloys have yield strengths that are approximately 2.5X higher than aluminum die casting alloys. ZA-27 is a cold chamber alloy with 27% aluminum which also makes it the lightest zinc die casting alloy. EZAC is a zinc die casting alloy with a unique combination of aluminum and copper which increases strength at lower melting temperatures.

Rigidity

Zinc alloys are rigid engineering materials. Their elastic moduli are greater than those of aluminum and magnesium alloys, and are an order of magnitude greater than those of plastic. This, combined with their high strength allows the volume of individual castings to be markedly reduced, saving space and weight.

Toughness and Ductility

High impact strength and good ductility are qualities of zinc alloys that are rarely found in most other casting alloys. Ductility is important for bending and crimpling in post-casting assembly operations, while impact strength provides performance in rough environments. Fracture toughness is also greater than for most aluminum alloys and cast irons.

Hardness

Compared to other competing materials such as aluminum and magnesium die castings, the ZAMAK alloys provide increased hardness and abrasion and wear resistance. Until recently, optimum hardness was provided by the cold chamber alloys ZA-12 and ZA-27 whose Brinell Hardness ranges from 95 to 122 when die cast. Today, Eastern manufactures a hot chamber zinc die casting alloy called EZAC whose hardness is approximately 125 Brinell. These values are much higher than the 70 to 85 BHN displayed by aluminum alloys, and much higher than the hardness values of engineered plastics.

Due to the higher hardness properties of zinc die casting alloys, components requiring improved wear or abrasion characteristics should be considered as a zinc die casting alloy. Significant cost savings opportunities are available if a hot chamber zinc die casting alloy is used.

Fatigue Strength

This measure of a material's ability to withstand cyclic loading is and important design criterion. All zinc die casting alloys have far better fatigue performance than plastic materials, and the zinc alloys with higher aluminum and copper (such as ZA alloys) compare favorably with aluminum die casting alloys.

Creep Strength

Due to the inherent low melting temperature of zinc and zinc alloys (which adds to the cost savings advantage of zinc die casting), Creep deformation has shown to be an issue with zinc die casting alloys at operating temperatures (combined with constant stress) approaching 200 deg F.

EZAC is a hot chamber zinc based alloy that has higher levels of copper and aluminum which has shown to have major improvements in creep performance compared to other zinc based alloys. Although still not as creep resistant as aluminum or magnesium die casting alloys, EZAC may be a smart economical choice if your current standard zinc alloy is not performing adequately, or when considering zinc for an application at higher temperatures and constant stresses. and unsure if the current zinc alloy will be adequate at higher operating temperatures or stresses.

Conductivity

As zinc alloys conduct both heat and electricity, they can be used for heat dissipating devices such as heat sinks. Zinc's excellent casting fluidity permits thinner fin and cooling pin design to better dissipate heat. Zinc's excellent electrical conductivity also provides good EMI, RFI and ESD shielding.

Non-sparking

Aluminum alloys can generate a spark when struck with a rusty iron component. All zinc alloys, except ZA-27, are classified as "non-sparking" and are the perfect low-cost alternative to bronze in potentially explosive environments.Zinc's non-magnetic properties are ideal for use in electronics and other applications where delicate moving parts are subject to magnetic disturbances.

Pressure Tightness

Soundness of castings is largely related to product design, tooling layout and process control. Die cast ZAMAK alloys, ZA-8 and ZA-12 are often used for pressure tight applications. For sand and permanent mold casting, ZA-12 is the preferred material. All zinc alloys solidify into a dense strong matrix with excellent pressure tightness.