There is no single “best” metal for die casting—only the most suitable metal for your specific application. The choice depends on four non-negotiable factors:
- Part function (e.g., structural load-bearing vs. decorative);
- Production volume (low-batch prototypes vs. high-volume mass production);
- Performance requirements (strength, weight, corrosion resistance);
- Cost constraints (material + tooling + post-processing).
Die casting relies on metals with low-to-moderate melting points (to avoid damaging steel dies) and high fluidity (to fill complex cavities). The four mainstream die casting metals—zinc alloys (Zamak), aluminum alloys, magnesium alloys, and copper alloys—each excel in distinct scenarios. Below is a systematic breakdown of their properties, applications, and tradeoffs.
1. Mainstream Die Casting Metals: Properties & Applications
This section details the most widely used die casting metals, with standardized performance data (per ASTM/ISO standards) and industry-validated use cases.
1.1 Zinc Alloys (Zamak Series: 3, 5, 7)
Zinc alloys are the most versatile and cost-effective die casting metals, accounting for ~40% of global die casting volume. They balance fluidity, strength, and machinability, making them ideal for small-to-medium parts.
Key Characteristics
|
Property
|
Zamak 3 (Most Common)
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Zamak 5 (High-Strength)
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Zamak 7 (Low-Lead)
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|
Composition
|
Zn (96.5%), Al (3.3%), Mg (0.05%), Cu (0.03%)
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Zn (95.5%), Al (4.0%), Mg (0.05%), Cu (0.5%)
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Zn (95.8%), Al (3.9%), Mg (0.05%), Cu (0.25%), Pb <0.004%
|
|
Melting Point
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380–420°C
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385–425°C
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380–420°C
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|
Tensile Strength
|
320 MPa (46,400 psi)
|
380 MPa (55,100 psi)
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350 MPa (50,800 psi)
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|
Density
|
6.6 g/cm³
|
6.7 g/cm³
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6.6 g/cm³
|
|
Corrosion Resistance
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Moderate (prone to white rust in saltwater)
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Good (Cu addition boosts resistance)
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Moderate (lead-free for RoHS compliance)
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Fluidity
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Excellent (fills 0.5mm thin walls)
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Very Good
|
Excellent
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|
Tooling Compatibility
|
P20/H13 steel (low wear)
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P20/H13 steel
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P20/H13 steel
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Advantages
- Lowest melting point (380–425°C): Reduces die wear (extends die life by 20–30% vs. aluminum) and energy costs.
- Superior fluidity: Captures fine details (e.g., 0.1mm engravings) for decorative parts.
- Cost-efficient: Material cost ((2.5–)3.5/kg) + tooling cost (30% lower than aluminum for small parts) = low per-unit cost for high volume.
Limitations
- High density: Not suitable for weight-sensitive applications (e.g., aerospace components).
- Low temperature resistance: Softens above 100°C (avoid engine bay or high-heat parts).
Typical Applications
- Consumer goods: Toy vehicles (1:24 die cast models), zippers, door handles, electronics housings (e.g., remote controls).
- Automotive: Interior components (air vent grilles, gear knobs), sensor brackets.
- Medical: Low-contact devices (e.g., wheelchair armrests—lead-free Zamak 7 for biocompatibility).
1.2 Aluminum Alloys (A380, A360, A413)
Aluminum alloys are the most widely used die casting metals (50% of global volume) for industrial and automotive applications. They balance strength, lightweight, and corrosion resistance—ideal for structural parts.
Key Characteristics
|
Property
|
A380 (Most Versatile)
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A360 (Corrosion-Resistant)
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A413 (High-Fluidity)
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|
Composition
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Al (92%), Si (7.5%), Cu (3.5%), Mg (0.1%)
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Al (95%), Si (5%), Mg (0.5%)
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Al (94%), Si (6%), Zn (0.3%)
|
|
Melting Point
|
580–650°C
|
590–650°C
|
585–640°C
|
|
Tensile Strength
|
310 MPa (45,000 psi)
|
280 MPa (40,600 psi)
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290 MPa (42,100 psi)
|
|
Density
|
2.7 g/cm³
|
2.7 g/cm³
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2.7 g/cm³
|
|
Corrosion Resistance
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Good (anodizable for outdoor use)
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Excellent (Mg addition for marine environments)
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Good
|
|
Fluidity
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Very Good (fills 0.8mm walls)
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Good
|
Excellent (for thin parts)
|
|
Tooling Compatibility
|
H13 steel (high wear resistance)
|
H13 steel
|
H13 steel
|
Advantages
- Lightweight: 60% less dense than zinc—critical for weight-sensitive parts (e.g., electric vehicle components).
- High strength-to-weight ratio: Outperforms zinc in load-bearing scenarios (e.g., automotive structural brackets).
- Temperature resistance: Maintains strength up to 150°C (suitable for engine bay parts).
Limitations
- Higher melting point: Increases die wear (H13 steel required, vs. P20 for zinc) and energy costs.
- Lower fluidity: Struggles with <0.8mm thin walls (needs precision tooling to avoid incomplete filling).
Typical Applications
- Automotive: Transmission housings, engine brackets, EV battery casings (A380), wheel hubs (A360).
- Industrial: Pump bodies, valve components, heat sinks (aluminum’s thermal conductivity = 150 W/m·K, 3x zinc’s).
- Outdoor: Lighting fixtures (A360 with powder coating for corrosion resistance), solar panel frames.
1.3 Magnesium Alloys (AZ91D, AM60B)
Magnesium alloys are the lightest die casting metals—used for high-performance, weight-critical applications. They are 33% lighter than aluminum but require specialized handling (flammability risk).
Key Characteristics
|
Property
|
AZ91D (Most Common)
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AM60B (High-Impact)
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|
Composition
|
Mg (90%), Al (9%), Zn (1%), Mn (0.1%)
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Mg (94%), Al (6%), Mn (0.1%)
|
|
Melting Point
|
590–650°C
|
600–650°C
|
|
Tensile Strength
|
230 MPa (33,400 psi)
|
270 MPa (39,200 psi)
|
|
Density
|
1.8 g/cm³
|
1.8 g/cm³
|
|
Corrosion Resistance
|
Poor (requires coating: e.g., chromate conversion)
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Moderate (higher Al boosts resistance)
|
|
Fluidity
|
Good (fills 1.0mm walls)
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Very Good
|
|
Tooling Compatibility
|
H13 steel (with anti-stick coating)
|
H13 steel
|
Advantages
- Ultra-lightweight: Enables fuel savings (automotive) or payload increases (aerospace).
- High impact resistance: AM60B outperforms aluminum in crash scenarios (used for EV door beams).
Limitations
- High cost: Material ((8–)12/kg) + specialized tooling (anti-flammability systems) = 2–3x more expensive than aluminum.
- Flammability risk: Molten magnesium ignites in air—requires inert gas (CO₂) during casting.
Typical Applications
- Aerospace: Drone frames, satellite components (weight reduction = launch cost savings).
- Automotive: EV seat frames, steering columns (AZ91D), crash structures (AM60B).
- Electronics: Laptop chassis (lightweight + rigid for portability).
1.4 Copper Alloys (Brass C36000, Bronze C95400)
Copper alloys (brass/bronze) are specialized die casting metals—used for parts requiring electrical conductivity or wear resistance. They have limited application due to high cost and processing challenges.
Key Characteristics
|
Property
|
Brass C36000 (Free-Cutting)
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Bronze C95400 (Aluminum Bronze)
|
|
Composition
|
Cu (60%), Zn (40%)
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Cu (85%), Al (10%), Fe (5%)
|
|
Melting Point
|
900–940°C
|
1020–1080°C
|
|
Tensile Strength
|
415 MPa (60,200 psi)
|
690 MPa (100,100 psi)
|
|
Density
|
8.5 g/cm³
|
7.8 g/cm³
|
|
Electrical Conductivity
|
45% IACS (International Annealed Copper Standard)
|
15% IACS
|
|
Tooling Compatibility
|
H13 steel (high wear—requires cooling)
|
H13 steel (with heat-resistant coating)
|
Advantages
- High conductivity: Brass C36000 is used for electrical connectors (e.g., terminal blocks).
- Extreme wear resistance: Bronze C95400 for high-friction parts (e.g., pump impellers, valve seats).
Limitations
- Highest melting point: Causes severe die wear (die life <50k cycles, vs. 500k for zinc).
- High cost: Material ((9–)15/kg) + tooling = only viable for high-value parts.
Typical Applications
- Electrical: Terminal blocks, circuit board connectors (brass C36000).
- Industrial: Hydraulic valve cores, marine propeller components (bronze C95400, corrosion-resistant in saltwater).
2. Decision Framework: How to Choose the Right Metal
Use this step-by-step process to align metal selection with your application—avoid costly mismatches (e.g., using zinc for high-heat parts).
Step 1: Define Part Function & Performance Needs
|
Part Type
|
Key Requirement
|
Recommended Metals
|
|
Decorative (e.g., toys, jewelry)
|
Fine detail, low cost
|
Zamak 3/7
|
|
Structural (e.g., brackets, housings)
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Strength, lightweight
|
Aluminum A380, Magnesium AZ91D
|
|
Weight-critical (e.g., drones, EVs)
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Low density, high strength
|
Magnesium AZ91D/AM60B
|
|
High-wear (e.g., valves, impellers)
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Wear resistance
|
Bronze C95400, Brass C36000
|
|
Outdoor/marine
|
Corrosion resistance
|
Aluminum A360, Bronze C95400
|
Step 2: Match to Production Volume
- Low volume (<10k units): Prioritize low tooling cost—Zamak 3 (P20 steel dies) or aluminum A380 (small single-cavity dies).
- High volume (>100k units): Prioritize per-unit cost—Zamak 5 (low material cost) or aluminum A380 (high production speed).
Step 3: Balance Cost & Performance
|
Budget Tier
|
Metal Option
|
Cost Breakdown (100k units)
|
|
Economy ($<5/part)
|
Zamak 3
|
Material: (2.5k + Tooling: )10k = $12.5k total
|
|
Mid-Range ((5–)15/part)
|
Aluminum A380
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Material: (8k + Tooling: )15k = $23k total
|
|
Premium ($>15/part)
|
Magnesium AZ91D/Bronze C95400
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Material: (20k + Tooling: )25k = $45k total
|
3. Common Myths & Misconceptions
Myth 1: “The strongest metal is the best choice.”
Fact: Strength is contextual. For a decorative toy, zinc’s lower strength is irrelevant—its detail reproduction and cost are more critical. For a structural EV bracket, aluminum’s strength-to-weight ratio outperforms “stronger” bronze (which is too heavy).
Myth 2: “Zinc is only for cheap, low-quality parts.”
Fact: High-grade Zamak 7 (lead-free) is used in medical devices and luxury consumer goods (e.g., high-end watch cases). Its fluidity enables precision that aluminum cannot match for small, detailed parts.
Myth 3: “Magnesium is too flammable to use safely.”
Fact: Modern die casting machines use inert gas (CO₂) to suppress ignition. Magnesium’s flammability risk is only present in molten form—cured parts are as stable as aluminum (used safely in millions of EVs and drones).
Myth 4: “Copper alloys are obsolete for die casting.”
Fact: Copper’s conductivity and wear resistance are irreplaceable for electrical and high-friction parts. For example, brass terminal blocks outperform aluminum in current-carrying capacity (critical for industrial wiring).
4. Industry Case Studies: Metal Selection in Practice
Case 1: Automotive EV Battery Casing
- Requirement: Lightweight (reduce vehicle weight), structural strength (protect cells), corrosion resistance (underbody exposure).
- Initial Choice: Zinc Zamak 5 (low cost) → Failed: Too heavy (added 15kg to vehicle weight) and poor corrosion resistance.
- Final Choice: Aluminum A380 (anodized) → Success: 60% lighter than zinc, 310 MPa tensile strength, and 5-year corrosion resistance in road salt.
Case 2: Drone Frame Production
- Requirement: Ultra-lightweight (max 200g), high impact resistance (crash survival), high volume (100k units/year).
- Initial Choice: Aluminum A380 → Failed: Too heavy (frame weight 250g, exceeding limit).
- Final Choice: Magnesium AZ91D → Success: Frame weight 180g, 230 MPa tensile strength, and 30% lower per-unit cost than carbon fiber (the alternative).
Case 3: Marine Valve Component
- Requirement: Corrosion resistance (saltwater), wear resistance (valve seating), high pressure (10 MPa).
- Initial Choice: Aluminum A360 → Failed: Wear rate too high (valve leakage after 6 months).
- Final Choice: Bronze C95400 → Success: No leakage after 2 years, 690 MPa tensile strength, and compatibility with seawater chemistry.
5. Conclusion: No “Best”—Only “Most Suitable”
The “best” die casting metal is determined by aligning its inherent properties with your application’s non-negotiable needs:
- Choose zinc alloys for low-cost, detailed, high-volume parts (toys, electronics).
- Choose aluminum alloys for lightweight, structural, industrial/automotive parts (brackets, housings).
- Choose magnesium alloys for weight-critical, high-performance parts (drones, EVs).
- Choose copper alloys for conductive, high-wear parts (electrical connectors, valves).
For complex applications (e.g., parts requiring both strength and detail), consider hybrid designs (e.g., aluminum structural core + zinc decorative overlay). Always validate metal selection with prototype testing (e.g., tensile testing, corrosion testing) and partner with die casters specializing in your target metal—their expertise will avoid costly rework.
For customized metal selection advice, share your part specs (function, volume, performance needs) in the comments, and we’ll provide data-backed recommendations.
