Zamak 3 vs Zamak 5 - Choosing the Right Zinc Alloy
Zamak 3 vs Zamak 5 compared: Zamak 5 gains 17% tensile strength and 45% compressive yield from copper, while Zamak 3 keeps higher ductility at lower cost.
Production Capabilities
Alloy and application photos for Zamak 3 vs Zamak 5
Die Casting Alloy
Material samples and cast components showcasing the alloy composition, grain structure, and as-cast surface quality.
Application Component
Finished die cast parts where this alloy delivers the required mechanical properties and performance in production.
Zamak 3 and Zamak 5 differ by exactly one element: copper. Zamak 3 has <=0.10% copper; Zamak 5 has 0.75-1.25%. That single difference produces measurable but focused property changes.
Composition Difference
| Element | Zamak 3 | Zamak 5 | Impact |
|---|---|---|---|
| Aluminum (Al) | 4.0% | 4.0% | Same |
| Copper (Cu) | <=0.10% | 0.75-1.25% | All property differences |
| Magnesium (Mg) | 0.04% | 0.04% | Same |
| Zinc (Zn) | Balance | Balance | Same |
Properties
| Property | Zamak 3 | Zamak 5 | Preferred |
|---|---|---|---|
| Tensile strength | 283 MPa | 331 MPa | +17% |
| Yield strength | 200 MPa | 228 MPa | +14% |
| Elongation | 10% | 7% | -0% |
| Hardness | 82 HRB | 91 HRB | +11% |
| Compressive yield | 414 MPa | 600 MPa | +45% |
| Impact strength | 58 J | 65 J | +12% |
| Creep resistance | Standard | Better | Measurable |
| Plating suitability | Excellent | Excellent | Same |
| Die life | Same | Same | Same |
| Cost | Baseline | +3-% | Small |
The Trade-Off in Plain Terms
Copper in Zamak 5 buys strength (+17% tensile, +45% compressive yield) at the cost of ductility (-0% elongation). For most applications, this favors Zamak 5 -the strength is valuable, the ductility reduction is inconsequential because zinc hardware is rarely designed to deform plastically in service.
For applications where ductility under assembly forces, snap-fit engagement, or drop impact is important, Zamak 3's higher elongation is the correct choice.
Creep -The Often-Overlooked Factor
Zinc alloys are susceptible to room-temperature creep (time-dependent deformation under sustained load). Zamak 5's copper reduces creep rate by 30-40% versus Zamak 3. This matters for:
- Parts with press-fit components that must maintain engagement force over years
- Loaded bearing surfaces where dimensional creep affects clearance
- Threaded insert housings where clamping load must be maintained
Decision Framework
| Application | Zamak 3 | Zamak 5 |
|---|---|---|
| Decorative furniture hardware | Yes | Yes |
| Padlock body (forced entry load) | - | Yes |
| Snap-fit assembly (ductility) | Yes | - |
| European architectural hardware | - | Yes(ZnAl4Cu1 is EU default) |
| Automotive seat hardware | - | Yes |
| Maximum plating quality | Yes | Yes(same) |
| Threaded insert housing | - | Yes(creep resistance) |
| Max volume economy | Yes | - |
North America: Zamak 3 is the default. Specify Zamak 5 when structural load, creep, or wear resistance is required.
Europe: Zamak 5 (ZnAl4Cu1 per EN 1774) is the default. Specify Zamak 3 only when maximum elongation or cost savings are the deciding factor.
Related Zinc Resources
- Zamak 3 — composition, properties, and applications of the default alloy
- Zamak 5 — the higher-strength copper-bearing alloy
- Zinc die casting alloys — full Zamak and ZA alloy selection guide
Related
Zinc alloy selection: casting@kastdiecast.com | +86 138 1403 4409
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