Zinc alloys used in die casting include Zamak 2, Zamak 3, Zamak 5, and ZA8. Zamak 2 has 3.8–4.3% aluminum, 2.7–3.3% copper, and 0.035–0.06% magnesium, with a tensile strength of 328 MPa. Zamak 3 is copper-free (<0.03%), has 3.8–4.3% aluminum, and 0.035–0.06% magnesium, with a tensile strength of 283 MPa. Zamak 5 contains 3.8–4.3% aluminum, 0.7–1.1% copper, and 0.035–0.06% magnesium, offering a tensile strength of 310 MPa. ZA8 has 8.2–8.8% aluminum, 0.9–1.3% copper, and 0.02–0.035% magnesium, with a tensile strength of 386 MPa and better thermal stability.

Want to see why large-volume Industries like automotive, consumer goods, or electronics choose them? Dive into this piece to learn how zinc alloys work and their benefits in detail.

Classification of Zinc Alloys

Zinc alloys fall under different categories. Since they have different primary alloying elements, their properties vary. That’s how you can determine their mechanical properties, casting behavior, and industrial components. Let’s discover the major ones.

Zamak 2 Alloy

Composition:

Zamak 2 contains zinc as a primary element. Also, there is 3.8–4.3% aluminum, 2.7–3.3% copper, and 0.035–0.06% magnesium. It has a higher amount of copper than other alloys. The hardness and wear resistance increase as a result.

Vlastnosti:

328 Mpa is the tensile strength of Zamak 2. The hardness goes from 100 HB. The higher amount of copper forms a stable alpha-beta brass phase.

It means these alloys have dimensional stability. Wherein you’re able to get accurate results from solidification.

Aplikace:

The components that deal with high-stress situations are made with zamak 2. For instance, gears, locks, and industrial machinery parts.

Binary eutectic phases wrap up zinc-rich dendrites. That is the unique feature of this alloy microstructure. This is also beneficial for wear resistance needs.

Zamak 3 Alloy

Composition:

Zamak 3 alloy consists of a lower amount of copper (<0.03%) along with 3.8 — 4.3% aluminum and 0.035 — 0.06% magnesium.

This alloy is distinguishable from other zamak alloys as there is almost zero presence of copper.

Vlastnosti:

The reason behind the superior ductility of Zamak 3 is its 283 MPa tensile strength and 20% elongation. The magnesium blend helps refine the grain boundaries of zinc. Consequently, a fine-grained structure avoids cracks during the cooling process.

Aplikace:

These alloys suit compact sizes or intricately shaped parts. For example, zippers, toy wheels, and electrical connectors.

Speaking about its microstructure, it features a more intricate dendrite. There is 20–40 μm space in dentrite compared to Zamak 2. So the alloys can cast highly specific parts.

Zamak 5 Alloy

Composition:

There is 3.8 — 4.3% aluminum, 0.7 — 1.1% copper, and 0.035 — 0.06% magnesium in the alloy of Zamak 5. Also, it has moderate copper content. That ranges between Zamak 2 and Zamak 3.

Vlastnosti:

Zamak alloys are ones that have balanced strength (310 MPa tensile) and castability. It also has a copper-aluminum intermetallic formation. That’s what copper addition does, increasing its hardness up to 91 HB.

Aplikace:

Zamak 5 goes well for manufacturing automotive components (door handles, carburetor parts) and hardware. Its composition structure gives better fluidity, resulting in less porosity.

ZA8 Alloy

Composition:

8.2 — 8.8% aluminum, 0.9 — 1.3% copper, and 0.02 — 0.035% magnesium are present in the ZA8 alloy composition. It is different from zamak alloys because of the excessive amount of aluminum.

Vlastnosti:

ZA8 operates at 120 °C. There is 386 Mpa tensile strength. 40% of this alloy microstructure is made up of aluminum-zinc eutectic phase. Another feature is to improve creep resistance.

Aplikace:

You can manufacture high-pressure cast parts with ZA8 alloy. For example, pump housings and brackets. It provides thermal stability as there are 50–80 μm spacing dendrites in its structure.

Superloy

Composition:

The superloy category of zinc consists of 6.6 — 7.2% aluminum, 3.2 — 3.8% copper, and <0.005% magnesium. The higher copper element of this alloy resembles brass. This is because it has the same pretension.

Vlastnosti:

Copper-aluminum content precipitates in getting 120 hardness in Superloy. It contains a mix of alpha and beta phases. That’s why their tensile strength is as good as 440 Mpa.

Aplikace:

This kind of zinc content is suited for casting heavy-duty parts like engine mounts and industrial tooling. It solidifies slowly. This means they promote dendritic structure as a result.

AcuZinc 5 Alloy

Composition:

2.8 — 3.3% aluminum, 5.0 — 6.0% copper, and 0.025 — 0.05% magnesium combinations form the AcuZinc 5 alloy. In comparison with most of the zinc alloys, it contains excessive copper content.

Vlastnosti:

The higher content of copper forms a copper-zinc matrix. That constitutes a tensile strength of 350 Mpa. The magnesium content exists to refine structures. It lessens shrinkage risk as well.

Aplikace:

This zinc metal is especially useful for making bearings and bushings. That’s utilized machinery setup. There is a ternary eutectic phase. This works to generate a low friction coefficient of up to 0.1–0.15.

Vlastnosti slitin zinku

Mechanické vlastnosti

The tensile of zinc-based alloys fluctuates between 283 Mpa (Zamak 3) and 440 MPa (Superloy). Its value of elongation is 10-20%.

Likewise, the alloy Zamak 5 archives 310 MPa tensile strength with a hardness of 91 HB.

Die-cast parts of zinc exhibit way better strength (15%) than those that are sand-cast. Sand casting also causes variants in shapes because it cools down early.

The ZA8 metal competes against heavy stresses. That makes it ideal for high-load applications like pump housings.

Odolnost proti korozi

The corrosion mechanism (shown in the image) depicts the electrochemical behavior of zinc alloys. Wherein zinc oxide at anodes (Zn → Zn²⁺ + 2e⁻).

The reason oxygen reduces is because of cathodes (O₂ + 2H₂O + 4e⁻ → 4OH⁻). When a protective layer forms, chloride ions (Cl⁻) produce soluble ZnCl₂. That disrupts this layer and causes pitting around 0.1-0.5 mm/year.

The presence of aluminum content in zinc metal (Zamak) stabilizes this shield. This is because of its ability to resist corrosion (30%).

Meanwhile, increases in dezincification risks in marine environments happen due to copper elements.

Thermal and Electrical Properties

In case of thermal expansion coefficient, zamak contains 23 × 10⁻⁶/°C (ZA8) to 29 × 10⁻⁶/°C. Addition of alloying elements changes the actual electrical conductivity or decreases it.

For instance, adding more copper in zamak 3 to form zamak 2 decreases from 28% IACS to 26%.

However, thermal stability around 110–125 W/m·K (below 100°C) of these alloys doesn’t change. Because of this, they are suitable for a wide variety of parts, including heat sinks.

Odolnost proti únavě

Each zinc metal alloy so far has had fatigue resistance limits. That fluctuates between 120 Mpa of zamak 3 to 180 Mpa of Superloy.

Casting techniques improve fatigue resistance by up to 20%. This is because it compresses residual stress.

Meanwhile, other techniques like machining need to work for stress relief annealing. So that they stop initially cracking

Zamak 2, 3, 5, ZA-8, Superloy, and AcuZinc 5 Comparison Table

Table 1: Nominal Composition Ranges (% by weight)

Table 2: Mechanical Properties (Typical Die-Cast Values)

Table 3: Physical Properties

Comparison of Zinc Alloy (Zamak 5) vs. Alternative Materials

Manufacturing Processes for Zinc Alloys

A.  Die Casting

Tlakové lití za tepla:

The process that can force molten zinc alloy into the die cavity to take on product profiles is a hot chamber tlakové lití zinku. It uses gooseneck and plunger systems to flow liquid.

This process goes well for casting metal with lower melting points. This is why it suits zinc. It completes its cycle times of 50-100 shots/hour.

Cold Chamber Die Casting:

The cold chamber casting isn’t like a hot chamber; it suits higher-melting-point alloys. There is a separate furnace to melt metal and manually pour it into the die.

It is much slower than hot chamber casting and may produce 20 to 40 shots per hour. However, there is less iron contamination in zinc-casting alloys.

B.  Gravity Casting

In the gravity casting process, metalworkers cool down the castings using natural convection. For this, they create cooling rates of 1-10 °C/s.

Coarse dendrites occur, which also lower the tensile strength compared to die-cast objects. This, however, maintains ductility and even works to improve it.

C.  Sand Casting

The most popular and easiest way of casting is sand casting. It needs less labor and just fewer key steps to cast zinc parts.

In this, the manufacturers pour molten zinc into the sanding die and wait until it cools  down. Then the die is opened to remove the finished part.

Sand molding takes many hours and cools slowly around 0.1–1 °C/s. That is the reason for large eutectic phase formation. The major benefits of ZA27 sand-cast parts are that they have better thermal stability than die-casting.

D.  Surface Finishing

Surface is very important regarding enhanced quality and properties of alloys. For example, electroplating (5-15μm zinc-nickel) stops corrosion 5 times better.

In case of getting a beautiful appearance, powder coating(50-80μm) is valuable. It also increases the number of alloys that survive 500+ hour salt spray tests like ASTM B117.

E.  Machining

The lead-free composition of zinc alloys like Zamak 3 offers 80% better machinability than free-cutting brass. It also lessens surface roughness by 0.8-1.6 μm Ra.

However, high-copper alloys that contain abrasive intermetallics, like Zamak 2, need carbide tools for machining.

F.   Recycling

Zinc alloys can be reused after their life span ends, as they contain 100% recyclable properties. They remelt at 420–450 °C. You can reduce dross occurrence up to <2% of melt weight by focusing on proper fluxing. The alloy can also maintain mechanical properties via  7+ remelting cycles.

Advantages of Zinc Alloys

Nákladová efektivita

Zinc alloys can save up to 40–60% compared to aluminum or stainless steel to fabricate compact-size parts. It usually costs 2.50−3.50/kg versus 5−8/kg for substitutes.

Also, the selection of die casting options brings its rate more down. But the prices vary based on the alloy types, projects or other manufacturing needs.

Odolnost proti korozi a trvanlivost

Zamak can survive above 500 hours in salt spray tests comparatively with mild steel (10x). For instance, the applications of marine-grade zinc corrode very low, up to <0.1mm/year in coastal environments.

Vysoký poměr pevnosti k hmotnosti

With good tensile strength, the parts of zinc alloys give 6.6-7.1 g/cm³ density. It enables comparable strength. That cast iron has a 7.2 g/cm³ density. For this, it operates at a 20% lower weight.

Damping Capacity

Zinc is useful for the fabrication of automotive mounts and machinery bases. This is because it can dampen 30% more vibrations than alternatives like aluminum. They reduce noise up to 15-20 dB.

Challenges and Limitations of Zinc Alloys

Corrosion Mechanisms

These alloys can have galvanic corrosion if nobler metals are present, like steel. The chloride-rich environments cause pitting (0.1–0.3 mm/year).

The alloys that consist of more aluminum struggle with intergranular corrosion above 60°C.

High-Temperature Performance

These alloys lose strength up to 40% when faced at 150°C (Zamak) and 60% at 200°C (ZA-8). Microstructural coarsening that occurs because of thermal cycling deviates dimensional shift per 100 cycles.

Toxicity Concerns

Exposure to zinc fumes results in metal fume fever. Also, OSHA ventilation is important for cadmium traces. There is a need for PPE with P100 filters and fume extraction while melting zinc.

Odolnost proti tečení

In ZA-27, creep strain reaches 0.5%, operating at 50 mpa after 1000 hours. Most of the complex designs reduce stress to yield strength. They use rib reinforcement to handle deformation.

Závěr

Zinc alloys serve a very important role in manufacturing various applications. It is cost-effective yet offers excellent castability and corrosion resistance. Like other metals, they have certain limitations, but they are versatile and recyclable. Ensure endurance across diverse industrial sectors with the metal of your choice.