Aluminum-Silicon Alloys for Die Casting
Aluminum-silicon alloys are the alloy family behind every aluminum die casting, containing 7.5 to 13% silicon to raise fluidity and cut solidification shrinkage. The aluminum-silicon eutectic sits at 12.6% silicon and 577 °C, and the production die casting grades cluster just below it: A380 at 7.5 to 9.5% silicon, A360 at 9.0 to 10.0%, ADC12 at 9.6 to 12.0% and A413 at 11.0 to 13.0%.
Aluminum-silicon alloys are the alloy family behind every aluminum die casting, containing 7.5 to 13% silicon to raise fluidity and cut solidification shrinkage. The aluminum-silicon eutectic sits at 12.6% silicon and 577 °C, and the production die casting grades cluster just below it: A380 at 7.5 to 9.5% silicon, A360 at 9.0 to 10.0%, ADC12 at 9.6 to 12.0% and A413 at 11.0 to 13.0%.
Everything else in the chemistry is a deliberate trade. Copper raises strength, hardness and machinability but costs corrosion resistance. Magnesium raises yield strength through Mg2Si but reduces ductility and increases dross. Iron is added on purpose to stop the melt attacking the die steel, and becomes harmful above about 1.3% where it forms brittle needle-shaped phases. Zinc is tolerated mainly so that secondary, recycled ingot stays economical.
The same four alloys carry different names in every standards system, which is why drawings arrive specifying A380, ADC10, EN AC-46000 or YL112 for what is functionally one alloy. This page covers the metallurgy behind the family and the cross-reference we work from when the drawing and the ingot certificate use different systems.
Capability at a glance
| Alloy family | Aluminum-silicon (Al-Si), AA 3xx.x and 4xx.x casting series |
|---|---|
| Silicon range in die casting grades | 7.5-13.0% |
| Al-Si eutectic composition | 12.6% silicon |
| Eutectic temperature | 577 °C |
| Maximum silicon solubility in aluminum | 1.65% at 577 °C |
| Production grades cast here | A380, ADC12, A360, A413 |
| European grades | EN AC-46000, EN AC-47100, EN AC-43400, EN AC-44300 |
| Tensile strength across the family | 296-324 MPa as cast |
| Density range | 2.63-2.74 g/cm³ |
| Thermal conductivity range | 96-121 W/m·K |
| Iron aim in the melt | 0.7-1.1% to prevent die soldering |
| Verification | Optical emission spectrometer on every ingot lot |
What are aluminum-silicon alloys?
Aluminum-silicon alloys are casting alloys in which silicon is the principal alloying element. In the Aluminum Association numbering system they occupy the 4xx.x series when silicon is essentially the only addition, and the 3xx.x series when copper or magnesium is added alongside it. A380 and ADC12 are 3xx.x alloys; A413 is a 4xx.x alloy. Every high pressure die casting alloy in commercial use belongs to this family.
The reason is straightforward: aluminum on its own is a poor casting metal. Pure aluminum contracts roughly 6.6% by volume on freezing, has a wide mushy zone under constraint and tears in a rigid steel die. Silicon fixes both problems at once. It raises fluidity so metal reaches thin sections before freezing, and because silicon expands slightly as it solidifies it offsets part of the aluminum contraction, cutting shrinkage and hot-tearing tendency.
That is also why wrought alloys cannot be substituted. 6061 contains 0.4 to 0.8% silicon and 7075 contains 0.40% maximum, which is far too little to feed a thin die casting; both hot tear in a constrained die and both solder to die steel because they lack the iron content that casting alloys carry deliberately. Wrought and cast aluminum alloys are not interchangeable grades of one material, they are two different classes of alloy designed for two different shaping processes.
Why silicon is added, and how much
Fluidity in casting terms is not viscosity, it is how far metal travels before enough solid forms in the stream to stop it. That distance depends on how much of the alloy is still liquid late in solidification, which in turn depends on how close the composition sits to the eutectic. As silicon rises toward 12.6%, the fraction of low-melting eutectic liquid rises with it and the metal keeps feeding thin sections for longer.
Silicon also changes what happens after the metal stops moving. Higher silicon content means less volumetric shrinkage, better surface detail reproduction, and lower hot-tearing tendency in constrained geometry such as a boss surrounded by a rib. It costs ductility and it makes the alloy abrasive to cutting tools, which is why the highest-silicon grades are the hardest to machine.
| Silicon content | Classification | Casting behaviour | Representative alloys |
|---|---|---|---|
| Below 2% | Dilute solid solution | Poor fluidity, wide mushy zone, tears in a rigid die; not castable under pressure | Wrought 6061 (0.4-0.8% Si), 7075 (0.40% max) |
| 5.0-7.0% | Hypoeutectic | Moderate fluidity with good ductility and weldability; suits sand and permanent mold, heat treatable | A356, A357 |
| 7.5-9.5% | Hypoeutectic | Wide process window and excellent fluidity; best machinability when alloyed with copper | A380, EN AC-46000, ADC10 |
| 9.0-11.0% | Hypoeutectic, approaching eutectic | High fluidity, low shrinkage, few interdendritic leak paths, so good pressure tightness | A360, EN AC-43400, ADC3 |
| 11.0-13.0% | Eutectic | Highest fluidity and lowest shrinkage, so the thinnest achievable walls; hardness rises and machinability falls | ADC12, A413, EN AC-47100, EN AC-44300 |
| Above 13% | Hypereutectic | Primary silicon crystals give wear resistance and low thermal expansion, but the alloy becomes abrasive and difficult to machine | 390, B390 (16-18% Si) |
Practical fluidity improves as composition approaches the 12.6% eutectic and then falls away above it, because primary silicon crystals begin forming early in the freeze and obstruct flow. That is why no common die casting alloy is hypereutectic unless wear resistance is the specific requirement.
Hypoeutectic, eutectic and hypereutectic behaviour
The aluminum-silicon system has a simple binary eutectic at 12.6% silicon and 577 °C, with a maximum silicon solubility in solid aluminum of only 1.65% at that temperature. Almost all the silicon in a die casting is therefore present as a separate phase rather than in solution, and how that phase forms is what distinguishes the three composition regimes.
Below 12.6% silicon the alloy is hypoeutectic. Primary aluminum dendrites nucleate first and grow as the melt cools, and the silicon-rich liquid between them freezes last as eutectic. The lower the silicon, the more dendrite structure forms early, and the sooner flow through a thin section is choked off. This is exactly why A380 at 7.5 to 9.5% silicon fills less readily than ADC12 at 9.6 to 12.0%.
At the eutectic composition the alloy freezes in a single reaction at essentially constant temperature, giving the narrowest freezing range, the best fluidity and the lowest shrinkage. A413 demonstrates this cleanly: 11.0 to 13.0% silicon with almost no copper gives a melting range of only 574 to 582 °C and the highest thermal conductivity of the four grades at 121 W/m·K.
Silicon content and freezing range are related but not the same thing, and copper is what separates them. ADC12 has near-eutectic silicon but 1.5 to 3.5% copper, and copper-bearing ternary eutectics depress its solidus to about 515 °C. Its fluidity still benefits from the high silicon, because plenty of liquid remains late in the freeze to feed thin walls, but that long freezing tail is also why copper-bearing grades need well-designed overflows to keep interdendritic shrinkage porosity out of sealing faces and machined areas.
Above 12.6% silicon the alloy is hypereutectic and primary silicon crystals form before the eutectic reaction. Those crystals are hard and give excellent wear resistance and low thermal expansion, which is why hypereutectic 390 alloys appear in engine blocks and compressor bodies, but they wreck machinability and are not used unless wear is the governing requirement.
What each alloying element does
The ranges below span the four production grades rather than any single specification, and every element in the list is there for a reason. The elements that look like contamination, iron, zinc and nickel in particular, are usually the result of a deliberate decision about die protection or feedstock economics rather than poor melt control.
| Element | Typical min % | Typical max % | Metallurgical role and trade-off |
|---|---|---|---|
| Silicon (Si) | 7.5 | 13.0 | Raises fluidity and cuts volumetric shrinkage from about 6.6% toward 4%; costs ductility and abrades cutting tools |
| Copper (Cu) | 0 | 4.0 | Strengthens through Al2Cu and improves machinability by helping chips break; each percent costs corrosion resistance and raises density |
| Magnesium (Mg) | 0 | 0.60 | Forms Mg2Si, raising yield strength, which is why A360 reaches 170 MPa; increases dross and reduces ductility above about 0.6% |
| Iron (Fe) | 0.6 | 1.3 | Added on purpose to stop the melt soldering to die steel; above 1.3% it forms brittle Al5FeSi needles that cut ductility and corrosion resistance |
| Manganese (Mn) | 0 | 0.55 | Converts needle-shaped iron phases into rounded alpha-Al(Fe,Mn)Si particles that are far less damaging |
| Zinc (Zn) | 0 | 3.0 | Tolerated so secondary ingot remains economical; contributes a little strength but worsens corrosion resistance and hot cracking |
| Nickel (Ni) | 0 | 0.55 | Mostly a residual from recycled feedstock; slightly improves strength at elevated temperature |
| Titanium (Ti) | 0 | 0.25 | Grain refiner, usually added as Al-Ti-B master alloy to reduce grain size and hot-tearing tendency |
| Strontium (Sr) | 0.01 | 0.03 | Modifies eutectic silicon from coarse plates to a fine fibrous form; matters less in die casting because rapid die cooling already refines the eutectic |
| Tin and lead (Sn, Pb) | 0 | 0.35 | Residuals from scrap, held low because both depress strength and corrosion performance |
| Aluminum (Al) | Balance | Balance | Base metal, typically 80 to 90% of the alloy depending on grade |
For the exact limits that apply to a specific grade, see the composition tables on the A380, ADC12 and A360 pages. Every incoming ingot lot is verified on an optical emission spectrometer against the supplier certificate before it enters the furnace.
European EN AC die casting grades
European drawings use the EN 1706 system, which gives each alloy both a numeric designation such as EN AC-46000 and a chemical designation such as AlSi9Cu3(Fe). The suffix in parentheses indicates the iron level appropriate to pressure die casting. The four grades below cover almost all European die casting work.
These grades are close to their ASTM and JIS counterparts but not identical, and copper is where the mismatches concentrate. Treating EN AC-47100 as interchangeable with standard ADC12 is the most common error we see, because the EN grade caps copper at 1.2% while ADC12 permits up to 3.5%.
| EN AC number | Chemical designation | Silicon % | Copper % | Magnesium % | Closest equivalents |
|---|---|---|---|---|---|
| EN AC-46000 | AlSi9Cu3(Fe) | 8.0-11.0 | 2.0-4.0 | 0.05-0.55 | A380, ADC10, YL112 — the European general-purpose grade |
| EN AC-47100 | AlSi12Cu1(Fe) | 10.5-13.5 | 0.7-1.2 | 0.35 max | ADC12 and A383, but with substantially lower copper |
| EN AC-43400 | AlSi10Mg(Fe) | 9.0-11.0 | 0.10 max | 0.20-0.50 | A360, ADC3, YL104 — corrosion and pressure-tight work |
| EN AC-44300 | AlSi12(Fe) | 10.5-13.5 | 0.10 max | 0.10 max | A413, ADC1, YL102 — thin walls and thermal conductivity |
| EN AC-46500 | AlSi9Cu3(Fe)(Zn) | 8.0-11.0 | 2.0-4.0 | 0.05-0.55 | EN AC-46000 with a higher zinc allowance for secondary metal |
Where a drawing names an EN AC grade as a specification requirement, we buy ingot to the EN chemistry and certify against EN 1706 rather than substituting the nearest ASTM or JIS alloy. Where the designation was inherited from an older drawing and the difference is not functionally relevant, we will say so in writing and quote the cheaper equivalent so the decision is yours.
Full standards cross-reference
One alloy, four names. The table below is the mapping we use when a customer drawing, an ingot certificate and an inspection report each refer to the same metal in a different system. The alloys in each row are close equivalents intended for the same applications, not identical specifications.
| Alloy family | ASTM B85 / AA | JIS H 5302 | EN 1706 | EN chemical | GB/T 15115 |
|---|---|---|---|---|---|
| Al-Si-Cu, general purpose | A380 / 380.0 | ADC10 | EN AC-46000 | AlSi9Cu3(Fe) | YL112 |
| Al-Si-Cu, high silicon | A383 / 383.0 | ADC12 | EN AC-47100 | AlSi12Cu1(Fe) | YL113 |
| Al-Si-Mg, low copper | A360 / 360.0 | ADC3 | EN AC-43400 | AlSi10Mg(Fe) | YL104 |
| Al-Si eutectic | A413 / 413.0 | ADC1 | EN AC-44300 | AlSi12(Fe) | YL102 |
Composition limits differ between systems, most often in copper, zinc and magnesium. Name the governing standard on your drawing and we will certify the chemistry against that standard rather than against whichever ingot happens to be closest.
Properties across the die casting alloy family
Read the table below as a set of trades rather than a ranking. Tensile strength spans only 296 to 324 MPa across the four grades, a spread of under 10%, and elongation barely varies at all, so strength is rarely the deciding factor. The properties that actually separate these alloys are corrosion resistance, pressure tightness, thermal conductivity, machinability and cost.
One relationship is worth naming explicitly, because it explains most of the table: copper content. Copper raises strength, hardness and machinability, and it lowers corrosion resistance, pressure tightness and thermal conductivity. A380 at 3.0 to 4.0% copper and A413 at 1.0% maximum sit at opposite ends of that single axis, and ADC12 and A360 sit between them.
| Property | A380 (AlSi8Cu3Fe) | ADC12 (A383) | A360 (AlSi10Mg) | A413 (AlSi12) |
|---|---|---|---|---|
| Ultimate tensile strength | 324 MPa (47 ksi) | 310 MPa (45 ksi) | 317 MPa (46 ksi) | 296 MPa (43 ksi) |
| Yield strength (0.2%) | 159 MPa (23 ksi) | 150 MPa (22 ksi) | 170 MPa (25 ksi) | 145 MPa (21 ksi) |
| Elongation in 50 mm | 3.5% | 3.5% | 3.5% | 2.5% |
| Brinell hardness | 80 HB | 75 HB | 75 HB | 80 HB |
| Silicon content | 7.5-9.5% | 9.6-12.0% | 9.0-10.0% | 11.0-13.0% |
| Copper content | 3.0-4.0% | 1.5-3.5% | 0.6% max | 1.0% max |
| Density | 2.74 g/cm³ | 2.70 g/cm³ | 2.63 g/cm³ | 2.66 g/cm³ |
| Thermal conductivity | 96 W/m·K | 96 W/m·K | 113 W/m·K | 121 W/m·K |
| Castability | Excellent | Excellent | Very good | Excellent |
| Corrosion resistance | Fair | Fair | Good | Good |
| Machinability | Very good | Good | Good | Fair |
| Pressure tightness | Good | Good | Excellent | Excellent |
| Relative cost | Lowest | Low | Moderate | Moderate |
Properties are typical as-cast values measured on separately cast test bars and will vary with wall thickness, gating and section geometry. Request a material certificate for lot-specific values.
Choosing an aluminum-silicon alloy
In practice the choice is driven by one dominant requirement, and the selection guide below maps the common ones onto a grade. Start from A380 and move away from it only when a specific requirement forces the move: thin walls push toward ADC12, corrosion and sealing push toward A360, and pure thermal performance pushes toward A413.
What the family cannot do is substitute for a wrought alloy. If a drawing calls for 6061-T6 or 7075-T6 properties, no aluminum-silicon casting alloy will reach them, and the part needs to be machined from billet instead.
- 6061 contains only 0.4 to 0.8% silicon, so it lacks the eutectic liquid needed to feed a thin section and it hot tears in a constrained steel die
- 7075 is an Al-Zn-Mg-Cu alloy with a wide freezing range and a strong tendency to crack during solidification under restraint
- Both wrought alloys solder aggressively to die steel because they lack the 0.6 to 1.3% iron that die casting alloys carry deliberately
- Wrought properties come from rolling or extrusion followed by solution treatment and ageing, none of which is available to a high pressure die casting because entrapped gas blisters at solution temperature
- Where 6061-T6 or 7075-T6 properties, bright anodizing or sub-500-piece volumes are the requirement, the part belongs in machined billet rather than in a casting alloy
| If your priority is | Recommended alloy | Why |
|---|---|---|
| Lowest piece price at volume | A380 | Best castability and tool life, widest supply, easiest to machine |
| Thin walls below 2 mm | ADC12 | Higher silicon improves flow into thin sections and long flow paths |
| Highest tensile strength | A380 | 324 MPa, the highest of the common die casting alloys |
| Highest yield strength | A360 | 170 MPa against A380's 159 MPa, despite slightly lower tensile strength |
| Corrosion resistance outdoors | A360 | Low copper content substantially improves corrosion performance |
| Pressure-tight or sealed housings | A360 | Excellent pressure tightness for hydraulic and IP-rated enclosures |
| Heat dissipation | A360 or A413 | Higher thermal conductivity than copper-bearing A380 |
| Heavy machining after casting | A380 | Highest machinability rating of the common die casting alloys |
| Asian supply chain alignment | ADC12 | JIS standard grade, most widely stocked alloy in Asia |
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Need machined aluminum parts instead of castings?
Die casting pays for itself above roughly 1,000 parts per year. Below that, or while you are still validating a design, CNC machining from billet is usually the faster and cheaper route. CharMax Precision runs a dedicated aluminum CNC machining operation for exactly that work, so you can prototype machined, then move to casting when volume justifies tooling.
Frequently asked questions
Why is silicon added to aluminum casting alloys?
Silicon is added to raise fluidity and cut solidification shrinkage. Pure aluminum contracts roughly 6.6% by volume on freezing and tears in a rigid steel die; silicon expands slightly as it solidifies, which offsets part of that contraction, and it lowers the freezing point toward the 577 °C eutectic so more liquid remains available late in solidification to feed thin sections. Practically, 7.5 to 13% silicon is what makes 1.5 mm walls, cast fins and fine surface detail possible at all. The costs are reduced ductility and increased abrasion of cutting tools.
What is the aluminum-silicon eutectic?
The aluminum-silicon eutectic is the composition at which the alloy freezes in a single reaction at one temperature: 12.6% silicon at 577 °C. Because silicon's maximum solubility in solid aluminum is only 1.65%, nearly all the silicon ends up as a separate phase. Below 12.6% the alloy is hypoeutectic and primary aluminum dendrites form first, with eutectic freezing last between them. Above it the alloy is hypereutectic and hard primary silicon crystals form first. Die casting alloys sit just below the eutectic because that is where fluidity is high and machinability is still acceptable.
What is EN AC-46000 equivalent to?
EN AC-46000 (AlSi9Cu3(Fe)) is the European equivalent of A380 in the ASTM system, ADC10 in JIS and YL112 in the Chinese GB/T system. All are aluminum-silicon-copper die casting alloys with roughly 8 to 11% silicon and 2 to 4% copper, used for general-purpose industrial castings. The permitted ranges for magnesium and zinc differ between systems, so if EN AC-46000 is a genuine specification requirement rather than an inherited designation we buy ingot to the EN chemistry and certify against EN 1706 rather than substituting standard A380 ingot.
Can 6061 or 7075 aluminum be die cast?
No. Both are wrought alloys and neither can be die cast. 6061 contains only 0.4 to 0.8% silicon and 7075 contains 0.40% maximum, far too little to feed thin sections, so both hot tear in a constrained steel die and both solder aggressively to die steel because they lack the deliberate iron content of casting alloys. Their published properties also depend on rolling or extrusion followed by solution treatment and ageing, and a high pressure die casting cannot be solution treated because entrapped gas blisters the surface. If a drawing specifies 6061-T6 or 7075-T6, the part must be machined from billet or extrusion.
Why do die casting alloys contain iron on purpose?
Iron prevents die soldering. Molten aluminum with low iron content dissolves iron out of the H13 die steel, welding casting to cavity and destroying both the part surface and the die. Holding 0.6 to 1.3% iron in the melt saturates the reaction and protects the tool, which is why casting alloy specifications allow iron levels that would be rejected in a wrought alloy. The limit exists because above roughly 1.3% iron forms brittle needle-shaped Al5FeSi phases that reduce ductility, machinability and corrosion resistance. We aim for 0.7 to 1.1% and add manganese, which converts those needles into rounded, less damaging particles.
Does high silicon content make die castings hard to machine?
Yes, and the effect is measurable rather than theoretical. Silicon particles are hard and abrasive, so tool wear rises with silicon content: A380 at 7.5 to 9.5% silicon rates very good for machinability, ADC12 at 9.6 to 12.0% rates good, and A413 at 11.0 to 13.0% rates fair. Hypereutectic alloys above 13% silicon require polycrystalline diamond tooling as a matter of course. None of these alloys is unmachinable, and we hold ±0.02 mm on machined features in all of them; the difference shows up as insert life and cycle time. Where a part has heavy machining, that argues for A380.
Are aluminum-silicon die castings heat treatable?
Not in high pressure die casting. Al-Si-Mg and Al-Si-Cu chemistries respond to solution treatment and ageing in principle, and A360 and A356 are heat treated routinely in permanent mold and sand casting. In a high pressure die casting the gas entrapped during injection expands at solution temperature near 500 °C and blisters the surface, so T6 is not available. Realistic options are a T5 stabilisation at lower temperature to relieve stress and stabilise dimensions, a geometry change to reduce stress, or a different casting process if heat-treated properties are genuinely required.
Is AlSi10Mg the same as A360?
They are close equivalents. AlSi10Mg is the chemical designation for the aluminum-silicon-magnesium casting family, and A360 is the ASTM B85 grade within it, with 9.0 to 10.0% silicon, 0.40 to 0.60% magnesium and copper capped at 0.6% maximum. The European die casting grade EN AC-43400 (AlSi10Mg(Fe)) is tighter, restricting copper to 0.10% and iron to 1.0%. Note that AlSi10Mg is also the standard aluminum powder for laser powder bed fusion, where the same chemistry reaches quite different properties because of the very high cooling rate, so check which process a published AlSi10Mg datasheet refers to.
Not sure which aluminum-silicon alloy your part needs?
Send your 2D drawing and 3D model with the service environment, sealing requirement or thermal target. We will recommend a grade, explain the trade-off in writing, and quote piece price and tooling against it.
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