A413 vs A380 Die Casting: How to Choose

A380 is the general-purpose choice: best balance of strength, castability, machinability, and cost. A413 is the pressure-tight specialist: slightly weaker, slightly more expensive, but with significantly better internal soundness. Choose based on whether pressure tightness is a design requirement.

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Composition and Properties Comparison

Parameter	A413	A380
Silicon	11.0-13.0% (near-eutectic)	7.5-9.5%
Copper	1.0% max	3.0-4.0%
Tensile strength	290 MPa	317 MPa
Yield strength	145 MPa	159 MPa
Thermal conductivity	121 W/m·K	96 W/m·K
Pressure tightness	Best - near-eutectic microstructure	Good
Porosity level (equivalent process)	Lower - finer solidification	Moderate
Machinability	Good	Excellent
Cost premium	~3-5%	Baseline

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Why A413 Has Lower Porosity

At A413's near-eutectic composition (12% Si, eutectic at 12.6%), solidification occurs with minimal dendrite formation - the microstructure is finer, shrinkage is lower, and inter-dendritic porosity channels are smaller and less interconnected. The result: reliably lower porosity per unit volume versus A380 in the same geometry and process conditions.

For a hydraulic manifold, the difference between Class 2 and Class 4 porosity (ASTM E505) can be the difference between passing and failing a 200 bar leak test.

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When to Choose A380

Choose A380 when the part needs a reliable balance of castability, strength, dimensional stability, machinability, and cost. It is often the safest starting alloy for industrial housings, automotive brackets, motor covers, gearbox cases, lighting housings, and electrical enclosures.

A380 is especially practical when:

1. The part is not carrying fluid or gas pressure.
2. Maximum tensile strength is needed (A380: 317 vs A413: 290 MPa).
3. Extensive CNC machining is planned (A380 machines better).
4. The project needs broad supplier familiarity and the lowest sourcing risk.

For many OEM sourcing programs, A380 reduces alloy-related uncertainty because it is widely used and easy to benchmark.

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When to Switch from A380 to A413

Switch to A413 when:

• Rated working pressure exceeds 80-100 bar and impregnation is not acceptable
• Helium leak test is required (<10^-5 mbar·L/s)
• Thermal conductivity is the design driver (121 vs 96 W/m·K - 26% better)
• Internal soundness certification to ASTM E505 Class 1-2 is required
• Thin walls or long flow paths make filling difficult, raising cold-shut and leakage risk

A413 is commonly considered for pump housings, valve bodies, compressor parts, hydraulic components, sealed covers, and thin-wall aluminum castings.

A380 is adequate when:

• No pressure tightness requirement
• Maximum strength and machinability are the priorities
• General structural or enclosure application

A413 is not a shortcut around poor tooling or process control. Gate design, venting, vacuum assistance, die temperature, machining allowance, and inspection planning still determine whether the finished part passes.

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Engineering Decision Table

Buyer requirement	Better starting point	Why
General housing with ribs and bosses	A380	Balanced properties and broad use
Thin-wall cover with long flow path	A413	Better fluidity for difficult filling
Pump or valve body with leak test	A413	Stronger pressure-tightness potential
Automotive bracket	A380	General mechanical balance and availability
Machined sealing surface	Depends on geometry	Alloy, porosity location, and machining allowance must be reviewed together
Lowest sourcing risk	A380	More common in global die casting supply chains

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DFM Questions Before Final Alloy Selection

Before locking A413 or A380, buyers should ask the supplier to review:

1. Minimum wall thickness and local thick-to-thin transitions
2. Flow length from gate to final fill area
3. Location of machined sealing faces
4. Leak test pressure and acceptance criteria
5. Porosity limits in critical zones
6. Surface finishing and coating requirements
7. Heat exposure during service
8. Annual volume and tooling budget

The right alloy decision should be made together with die design, gating, venting, machining, and inspection planning.

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Common Mistakes

• Selecting A413 only because the part is aluminum, without leak or filling requirements
• Selecting A380 for a pressure-tight part without reviewing porosity risk
• Moving sealing faces into areas likely to contain trapped air
• Defining leak testing after tooling is already built
• Ignoring coating buildup on gasket faces and threaded holes
• Treating alloy choice as a substitute for vacuum, venting, or DFM

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The Cost Calculation

A413 costs ~3-5% more per kg than A380. On a 1 kg casting at $3.00/kg material: $0.09-0.15/part premium. If this switch eliminates:

• Pressure test rework cycles: $1-2/part
• VPI impregnation post-process: $1-2/part
• Field leakage warranty returns: $20-100/part returned

The alloy switch pays for itself on the first quality event it prevents.

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FAQ

Is A413 stronger than A380?

Not necessarily in the way buyers usually mean. A380 is often selected for its balanced mechanical profile (317 MPa tensile), while A413 is selected for fluidity and pressure-tight casting potential. The better alloy depends on the part function.

Is A413 better for leak-tight die castings?

A413 is often a strong candidate for leak-sensitive aluminum die castings because of its castability and near-eutectic fluidity. Final leak performance still depends on die design, venting, process control, machining location, and testing.

Can I replace A380 with A413 without changing the tool?

Sometimes, but it should not be assumed. Alloy changes can affect filling, shrinkage, machining behavior, surface finish, and inspection results. Review the tool and quality requirements before switching.

Which alloy is better for aluminum housings?

A380 is usually the better starting point for general aluminum housings. Review A413 when the housing has thin walls, long flow paths, sealed cavities, or leak testing requirements.

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KastMfg can review A413, A380, A360, A390, and ADC12 options during DFM so the alloy decision matches the tooling, machining, finishing, and inspection plan. Send your drawing for a free alloy review.

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