What are the most common aluminum alloys used in die casting?

The short answer

Die casting alloys are a separate family from wrought aluminium

The aluminium in a die casting is not the aluminium in an extrusion or a machined block, and the difference is deliberate. Wrought alloys such as 6061 and 6063 contain only about 0.4 to 0.8 percent silicon and have a wide freezing range. Poured into a steel die at high velocity they hot-tear and stick, which is why a drawing that specifies 6061-T6 belongs in machining or fabrication rather than in a casting quotation. Casting alloys raise silicon to 7 to 13 percent, sometimes 17, which lowers the melting range, sharpens the freezing interval and makes the melt flow far enough to fill thin ribs before it sets.

The second structural point is that aluminium must run in a cold-chamber machine. At around 690 C the melt dissolves iron out of a submerged gooseneck, so hot-chamber injection belongs to zinc and magnesium only. Everything below therefore assumes a cold chamber, a die in H13 tool steel and a wall in the 1 to 4 mm range.

The grades you will actually be quoted

Composition is the fastest way to tell the grades apart, because every element is there for a reason. Silicon buys fluidity and wear resistance. Copper buys strength and hardness and costs corrosion resistance and bright anodising. Iron, held around 0.6 to 1.0 percent, stops the casting soldering itself to the die. Magnesium refines the structure and, at higher levels, makes the alloy heat-treatable.

Silicon, copper and iron: what each element buys

Reading a certificate of analysis is the skill that separates buyers who get what they asked for from buyers who get what was in the furnace. Silicon is the fluidity budget, and increasing it from 8 to 12 percent is what allows a 1.2 mm wall to fill over a long flow path. The cost is machinability and die wear, which is why a 17 percent silicon alloy such as B390 machines like a different material altogether and shortens die life. Copper is the strength budget: A380 carries roughly 3 percent and A360 less than 0.6 percent, and that single difference is what makes A360 the choice for anything that lives outdoors.

Two trace elements quietly decide whether a run goes well. Iron is a nuisance in most metallurgy, but in die casting it reduces die soldering and raises hot strength, which is why specifications permit it up to roughly 1.0 to 1.3 percent. Zinc is the opposite: it improves castability but above about 1.5 percent it promotes hot shortness, so A380 caps zinc at about 3 percent and a contaminated melt becomes brittle. Both are worth checking heat by heat rather than relying on a generic data sheet.

How to pick a grade in four steps

The order matters, because each step eliminates options that the next step cannot rescue.

1. Apply the process limits. High-pressure die casting only, which means the alloy must come from the casting family. Confirm the wall is between about 1.0 and 4 mm and that the part fits the machine.
2. Check the filling requirement. Long, thin flow paths need 10 to 12 percent silicon. Compact thick parts do not, and paying for fluidity that is not needed costs machining time and die life.
3. Check the service conditions. Salt spray or outdoor exposure pushes you to the low-copper grades. Wear surfaces push you towards high silicon. Anything that must hold pressure pushes you towards a more eutectic alloy.
4. Decide the finish last. If the part must be bright anodised, copper is the enemy and A360 or A413 is the answer. If it will be powder coated, plated or left as-cast, copper is free to do its job.

Where the grades are not interchangeable

• 6061 and 6063 cannot be die cast. Their low silicon content and wide freezing range produce hot tears in a steel die. If the drawing says 6061-T6, the part needs machining or fabrication, not a casting quotation.
• A380 will not anodise bright. Its roughly 3 percent copper produces a mottled dark grey film. Buyers expecting the appearance of anodised 6061 are reliably disappointed. Specify A360 or A413 at design stage, because changing alloy after tooling is cut can require re-engineering the gates.
• A356 belongs to permanent mould, not pressure die casting. It is the grade for heat-treatable structural castings, poured at lower velocity so that it can take a T6 treatment without blistering.
• Standard die castings cannot be solution treated. Gas entrained at 30 to 50 m/s gate velocity expands above 500 C and blisters the surface. Use T5, or specify vacuum-assisted casting where the load case genuinely needs more strength.
• Secondary operations still apply. As-cast linear tolerance is around plus or minus 0.13 mm on good features; bores, sealing faces and bearing fits are machined afterwards to plus or minus 0.02 to 0.05 mm.

Designations, equivalents and certificates

The same alloy arrives under at least four naming systems, and it is worth recognising them before comparing quotations. The American system uses AA numbers such as A380 and A383. The Japanese JIS system uses ADC10 and ADC12. Europe uses EN AC numbers such as EN AC-46000 and EN AC-43400. Older British and Commonwealth drawings use LM designations, where LM24 is close to A380 and LM6 is close to A413. Chinese supply usually quotes GB YL113. None of these is a lesser grade, but the permitted ranges differ slightly between them, so a quotation that says only ADC12 is not the same as one that names the standard.

Ask for a spectrographic certificate per heat rather than a generic data sheet. The elements that change how the melt behaves are exactly the ones that drift: silicon shifts fluidity, copper shifts strength, and iron and zinc shift both soldering behaviour and machinability. A generic sheet tells you what the alloy should be, not what was poured.

How we choose the alloy for a part

We cast aluminium and zinc and machine the critical features in house, so the recommendation follows the part rather than the ingot we happen to have in stock. Send the STEP file or drawing with the load case, the environment, the annual volume and any cosmetic requirement, and we will come back with a grade, the wall and tolerance expectations, the draft and gate position, and DFM feedback on where porosity is likely. Where two grades are viable we will price both, because the cheaper alloy is not always the cheaper part once machining and finishing are counted. See aluminium die casting, surface finishing for the anodising and coating options and metal stamping for the sheet-metal alternative at lower volume.