How to Choose the Right Aluminum Alloy for Your Die Casting Project

Why your alloy choice matters more than it appears

Alloy selection rarely gets the deliberate attention it deserves. A drawing arrives specifying “A380” or “ADC12,” the reasoning behind it long since lost, and so the default becomes whichever alloy your supplier happens to cast most often. That works well enough, right up until the application runs into its limits.

The choice you make governs far more than material cost, which is in fact the least significant factor of all. It determines how cleanly a part fills a complex mold, which surface treatments are viable, how the part behaves during later machining, and whether it performs reliably once it’s in service. Getting the alloy right at the specification stage saves you costly rework and improves yields, and it tends to deliver a lower total cost per part than a decision made on price alone.

This guide looks at the five aluminum alloys most commonly specified for die cast components: A380, A383/ADC12, A360, B390, and A413. The property data throughout is drawn from the North American Die Casting Association (NADCA) 2021 Product Specification Standards.

The five alloys and their respective strengths

A380: the general-purpose standard

A380 is the most widely specified aluminum die casting alloy in North America, and that broad adoption is well founded. The NADCA 2021 data records a composition of 7.5 to 9.5% silicon and 3.0 to 4.0% copper, with iron held to a maximum of 1.3%. In the as-cast condition it gives you 324 MPa ultimate tensile strength, 159 MPa yield strength, and 3.5% elongation.

Its appeal lies in balance. NADCA rates it 2 of 5 for die filling, where 1 is the best score, so it fills most geometries reliably. It earns a 1 for both anti-soldering and electroplating ease, which makes it a strong candidate wherever plated finishes form part of the design. And its machining rating of 3 sits comfortably above average for the aluminum group.

The principal limitation is corrosion resistance, rated 4 of 5, where 5 is least desirable. This follows directly from the copper content. Copper improves strength and machinability, but it reduces resistance to salt spray and moisture. A380 parts intended for outdoor service or sustained humidity will therefore need protective surface treatment to perform over time.

A383 / ADC12: for thin walls and fine detail

A383 is the ANSI/AA designation. Most Asian foundries know the alloy as ADC12 under the Japanese Industrial Standard. The two are closely related but not identical: ADC12 permits slightly different iron and zinc limits under JIS, while NADCA’s A383 specification sets copper at 2.0 to 3.0%, silicon at 9.5 to 11.5%, and magnesium at a maximum of 0.10%.

NADCA treats A380, 383, and 384 as substantially interchangeable when it comes to mechanical properties. A383’s 310 MPa tensile strength and 152 MPa yield are marginally lower than A380’s figures, but the difference is too small to affect most applications.

Where the alloy really distinguishes itself is castability. It earns a rating of 1 for die filling, the best possible score, reflecting its higher silicon content and improved fluidity. In practice this means it fills intricate geometry and thin-wall sections more reliably than A380. It also rates better on corrosion resistance (3 against 4, owing to its lower copper content) and on machining ease (2 against 3).

For components sourced in Asia, ADC12 is the practical default. It accounts for the majority of aluminum die casting output across Japan, Taiwan, and China, so supplier experience, process optimization, and material availability all favor it within the region.

A360: for corrosion resistance and thermal performance

A360 has a fundamentally different composition. Its primary strengthening element is magnesium (0.4 to 0.6%) rather than copper, which is held to a maximum of 0.6%. That makes it considerably more corrosion-resistant, rated 2 against A380’s 4.

It also offers superior thermal conductivity at 113 W/mK, compared with A380’s 96.2 W/mK. For a component that has to dissipate heat, such as an LED driver housing or a motor enclosure, that difference is meaningful. NADCA rates it 1 for strength at elevated temperatures, the best result in the standard aluminum group.

The trade-off is castability. A360 scores 3 for die filling, and NADCA describes it as offering higher corrosion resistance and better ductility at the cost of more difficult casting. It demands greater tooling and process expertise, and it’s less suited to high-volume production where cycle time is the priority.

B390 / ADC14: for wear resistance

For a component that operates under continuous friction, B390 is worth a look. It contains 16.0 to 18.0% silicon, the highest of any standard die casting alloy, together with 4.0 to 5.0% copper. That silicon content produces free silicon crystals within the structure that act as a hard bearing material, giving B390 a hardness of 120 BHN against the 80 BHN typical of A380. The 2021 NADCA data notes that it was developed for engine blocks and is used in valve bodies and sleeveless piston housings.

The trade-offs are significant. Ductility falls below 1%, which makes the alloy brittle relative to the others in this group. NADCA rates it 5, the least desirable score, for both machining ease and polishing quality, so finishing operations cost more and tool wear runs higher. It also rates 4 for hot cracking resistance, which means it needs strong process control from the supplier to cast reliably. B390 suits a specific class of high-wear application, and you should specify it only where wear resistance is the primary design driver.

A413 / ADC1: for pressure tightness

A413 is the alloy to specify where a component has to contain fluid or gas under pressure. It contains 11.0 to 13.0% silicon, with copper held to a maximum of 1.0%, and NADCA rates it 1 for both pressure tightness and hot cracking resistance, the best possible scores in each category. It also rates 1 for die filling, which makes it well suited to castings that must be both intricate in geometry and leak-free in service. Hydraulic cylinders, fluid manifolds, and pressure vessels are typical applications.

Its thermal conductivity of 121 W/mK is also higher than A380’s 96.2 W/mK, so it performs well where heat dissipation matters alongside pressure integrity. The limitations are machining ease (rated 4) and polishing quality (rated 5), both a consequence of the high silicon content. A design that needs significant post-casting machining or a polished decorative finish will run up higher finishing costs with A413. But for functional pressure-containing components where appearance is secondary, it’s one of the most capable alloys available.

A summary for selection

The appropriate choice depends on part geometry, operating environment, surface treatment requirements, and the region of manufacture. The following summary is based on NADCA’s 2021 characteristic ratings.

Choose A380 / ADC10 when

• The application is general-purpose, with no harsh or corrosive exposure
• Electroplated finishes are required (rated 1, best in class)
• The geometry has no thin walls or highly intricate features
• You are sourcing from North American or European suppliers

Choose A383 / ADC12 when

• The part has thin walls, complex internal geometry, or fine surface detail
• Moderate corrosion resistance with appropriate surface treatment is acceptable
• Post-casting machining requirements are significant
• You are sourcing in Asia, where ADC12 is the regional standard

Choose A360 / ADC3 when

• The part will operate in a corrosive, marine, or high-humidity environment
• Thermal dissipation is a primary requirement
• The application involves elevated operating temperatures
• Pressure tightness is a functional requirement

Choose B390 / ADC14 when

• The component operates under continuous friction or wear (engine cylinders, valve bodies, pump housings)
• Hardness is more important than ductility or ease of machining
• Your supplier has documented experience with hypereutectic alloys
• You have reviewed machining costs and accounted for higher tool wear

Choose A413 / ADC1 when

• The component must contain fluid or gas under pressure (hydraulic cylinders, fluid manifolds)
• Intricate geometry and pressure tightness are both required
• Thermal conductivity matters alongside pressure integrity
• A functional rather than decorative finish is acceptable

Selecting the alloy is only the first stage

Once the alloy is settled, the next thing to get right is sourcing it correctly across regions, because the same alloy carries a different designation under each standards body, and your choice also sets limits on surface treatment and heat treatment downstream. Both are covered in the companion article: a cross-border sourcing guide to die casting alloy names and downstream processes.

At Joincast, we work with you from the specification stage to make sure your alloy choice aligns with both the performance your part requires and the full downstream process: CNC machining, surface treatment, and quality inspection. If you have a component in development or an existing specification under review, contact us to discuss your requirements.

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