What materials are commonly used in die casting?

The short answer

The four families at a glance

Die casting only works with non-ferrous alloys that melt low enough to spare the hardened steel die. That single constraint excludes steel and cast iron and leaves the four families below, each with a distinct reason to exist. The table is the fastest way to place a part in the right family before arguing about grade.

Aluminium alloys: the workhorse family

Aluminium is chosen when you need a combination rather than a single property: reasonable strength at low weight, good thermal conductivity, acceptable as-cast tolerance and a mature supply chain. Within the family, the choice is narrower than it first appears.

• ADC12 and A380. The global workhorse, containing roughly 8 to 9.5 percent silicon and 3 to 4 percent copper. ADC12 is the Japanese and Asian designation for essentially the same alloy family. Tensile strength as-cast is around 250 to 320 MPa with 1 to 3 percent elongation, and fluidity is excellent, which is why it fills thin ribs and complex bosses reliably.
• A383. A close variant with slightly better fluidity and surface finish, used for thin-walled or decorative parts where fill quality matters more than peak strength.
• A360. Higher corrosion resistance and better pressure tightness than A380, so it suits parts that must not leak, including hydraulic and fluid-handling bodies.
• A356 (Al-Si-Mg). More ductile and heat treatable. In the T6 condition it reaches roughly 330 MPa with dramatically better elongation, which is why structural and safety-related parts use it rather than A380.
• B390. Around 17 percent silicon for wear resistance, used for bearing surfaces, compressor housings and pump bodies. It is abrasive to the die, so die life falls and cost rises.

Zinc alloys and thin-wall precision

Zinc is the low-temperature family, and that has practical consequences. Zamak 3 melts around 380 to 390 C, so it runs in a hot-chamber machine with cycle times measured in seconds and much lower thermal load on the die. The result is a die life that commonly runs from 500,000 to a million shots against roughly 200,000 to 350,000 for aluminium, and a wall capability down to about 0.4 mm, against roughly 1.2 mm for aluminium over a limited flow length.

Zamak 3 is the general-purpose grade with the best combination of castability and cost. Zamak 5 adds roughly 20 percent to tensile strength and is used where the part carries a load. Both cast and machine beautifully, take plating well, and are used for lock hardware, electronic enclosures, camera frames and small precision components. The trade-off is weight: at 6.6 grams per cubic centimetre, zinc is more than twice as dense as aluminium, so it is rarely the right answer for anything large.

Magnesium, when weight is the driver

Magnesium is the lightest structural die-casting metal at about 1.8 grams per cubic centimetre, roughly a third lighter than aluminium for the same volume, with tensile strength of 225 to 320 MPa and excellent electromagnetic shielding. That combination is why AZ91D and AM60B appear in laptop and camera bodies, drone frames, instrument panels and lightweight vehicle structures. AM60B is the more ductile of the two and is used where impact resistance matters.

The costs are real. Magnesium is more expensive than aluminium, it needs a protective atmosphere during melting because the melt oxidises and can ignite, and it has the worst natural corrosion resistance of the three main families, with a salt-spray endurance measured in tens of hours rather than hundreds. Magnesium parts essentially always receive a coating, typically micro-arc oxidation or an electrophoretic finish, and that coating should be costed into the business case rather than treated as optional.

Copper and brass, for conduction and wear

Copper alloys are the small, specialist end of die casting. C36000 free-cutting brass and C83600 and C95400 bronzes offer thermal and electrical conductivity two to three times that of aluminium, plus high hardness and good wear resistance, which makes them the standard choice for electrical connectors, heat-sink inserts, valve bodies and tapware components. The problem is temperature: with melting points from roughly 880 to 1,100 C they are far harder on the die than aluminium, tool life is short and tooling cost is high. Copper die casting is specified for performance, almost never to save money.

Alloy limits and what rules a material out

Knowing the limits saves more money than knowing the advantages. These are the constraints that most often force a change of family after a part has already been designed.

• Ferrous metals cannot be die cast. Steel and cast iron melt far above the temperature the die can survive, and the same applies to titanium. Those parts belong in investment or sand casting, or in machining.
• Wrought alloys such as 6061 are unsuitable. The alloying is optimised for extrusion and machining, not for high-velocity fill, and it tends to hot-crack and stick to the die.
• Wall thickness has a window, not just a minimum. Aluminium works best between about 1.5 and 4 mm and becomes difficult above roughly 8 mm, because solidification time scales with the square of section thickness and thick sections shrink into internal porosity.
• Porosity is inherent to high-pressure fill. Trapped gas and shrinkage voids limit weldability and rule out conventional heat treatment of standard castings. Vacuum-assisted machines reduce it but add cost.
• Bearing bores and sealing faces should be machined. As-cast tolerance is around plus or minus 0.1 to 0.25 mm; secondary machining takes critical features to plus or minus 0.02 to 0.05 mm.
• Volume has to justify tooling. Below roughly 3,000 to 5,000 parts, the tooling amortisation usually makes machining or sand casting cheaper overall.

Material selection at SOMI

We cast aluminium and zinc alloys and machine the critical features afterwards, so the recommendation we give is based on the part rather than on what a single machine happens to run. Send the drawing or the STEP file with the load case, the environment and the annual volume, and we will come back with the alloy, the wall and tolerance expectations, the tooling position and the price at two volumes so the break-even is visible. See aluminium die casting, surface finishing for the coating options and plastic injection moulding if the part does not need metal.