Aluminum Alloy AlSi9Cu3 (EN AC-46000) Cast Aluminum

What is AlSi9Cu3 / EN AC-46000 cast aluminum?

AlSi9Cu3 (also written EN AC-46000 or GD-AlSi9Cu3(Fe)) is a hypoeutectic Al-Si-Cu casting alloy standardized in EN 1706. It contains about 9% silicon and 2–4% copper, with controlled additions of Fe, Mn, Mg, Zn and other elements.

The alloy is optimized for high-pressure die casting of thin-wall, complex parts that need:
– very good castability and filling ability
– moderate strength and hardness at room and elevated temperatures
– good machinability and polishability

In practice, when a drawing says “Material: AlSi9Cu3, EN AC-46000, HPDC”, it almost always refers to a high-pressure die-cast aluminum component used in applications such as automotive engine and transmission housings, pump and valve bodies, gearbox casings, and structural brackets.

Is AlSi9Cu3 the same as EN AC-46000 or 46000-F?

These names all point to the same alloy system, just from different standards or notations:

• EN AC-46000 – EN 1706 designation (European aluminum casting standard)
• EN AB / EN AC-46000 – older EN notation; “AB”/“AC” may appear in datasheets
• GD-AlSi9Cu3(Fe) – German DIN style for pressure-die-casting (“GD”) with controlled Fe
• AlSi9Cu3 – chemical shorthand used on drawings and in research papers
• 46000-F – used by some databases for the as-cast (“F”) condition

Occasionally you’ll also see typos such as “AISi9Cu3” – they usually refer to the same AlSi9Cu3 alloy.

When you’re sourcing parts, the key is to check that your supplier confirms:
“We cast to EN 1706 EN AC-46000 / AlSi9Cu3 for high-pressure die casting.”

Key chemical composition of AlSi9Cu3 (EN AC-46000)

Typical composition ranges (approximate, for reference only):

• Silicon (Si): ~8–11 % – improves castability, reduces shrinkage
• Copper (Cu): ~2–4 % – increases strength and hardness, especially at higher temperatures
• Iron (Fe): up to ~1.3 % – controlled to avoid excessive Fe-rich intermetallic needles
• Manganese (Mn): ~0.2–0.6 % – helps neutralize Fe and improve toughness
• Magnesium (Mg): small addition – contributes slightly to strength
• Zinc (Zn), Nickel (Ni), Titanium (Ti), others: minor elements within low limits
• Aluminum: balance

What this means for design

• The Si + Cu combination gives good casting behavior plus higher strength than simple Al-Si alloys.
• Controlled Fe/Mn balance limits brittle intermetallic phases, improving impact and fatigue performance.
• The alloy is not designed for welding or anodizing; coatings or painting are usually preferred for corrosion protection.

Always check the specific foundry certificate or EN 1706 table when you need exact limits for PPAP, material approval, or FEA input.

Mechanical & physical properties – how strong is AlSi9Cu3?

Property ranges will depend on casting process, section thickness, and test standard, but typical values for high-pressure die-cast EN AC-46000 are in the following order of magnitude:

Room-temperature mechanical properties (as-cast / lightly aged)

• Ultimate tensile strength (UTS): ~230–270 MPa
• 0.2% Yield strength: ~130–170 MPa
• Elongation (A): ~1–3 % (often closer to 1 % in thin-wall HPDC parts)
• Brinell hardness: ~80–110 HB

Physical & thermal properties

• Density: ~2.7–2.8 g/cm³
• Thermal conductivity: roughly 100–180 W/m·K (moderate for cast aluminum)
• Coefficient of thermal expansion: ~21–23 µm/m·K
• Electrical conductivity: lower than pure aluminum, but adequate for housings and structural parts

Implications for engineers

• You get higher strength than many pure Al-Si alloys (e.g. simple AlSi10Mg) at the cost of slightly lower ductility.
• The alloy handles moderate operating temperatures (e.g. engine surroundings, gearbox housings), but is not a high-temperature alloy like some special Al-Si-Cu-Ni grades.

Where is AlSi9Cu3 aluminum used in die casting?

Because of its balance of castability, strength, and cost, AlSi9Cu3 is widely used in:

Automotive & transportation

• Engine blocks and cylinder heads (for some designs)
• Transmission housings and gearboxes
• Pump and compressor housings
• Clutch, brake and steering system components
• Structural brackets and mounts

Industrial equipment

• Hydraulic and pneumatic housings
• Gear cases, pump bodies, valve bodies
• Motor housings and fan covers
• Heat-dissipating housings where moderate thermal conductivity is enough

Energy & electronics

• Inverter and converter housings
• Cooling channel blocks and heat-spreading structures
• Die-cast enclosures with integrated fins and ribs

Whenever you need complex geometry, thin walls, and moderate mechanical loads, AlSi9Cu3 is usually on the shortlist.

Why do designers like AlSi9Cu3 for complex die-cast parts?

From a design-for-manufacturing (DFM) perspective, AlSi9Cu3 offers several advantages:

1. Excellent high-pressure die-castability
   • Fills thin sections and long flow lengths well
   • Good resistance to hot tearing when gating and cooling are properly controlled
2. Stable mechanical performance
   • Sufficient strength for many structural housings and brackets
   • Copper content keeps strength at an acceptable level at moderately elevated temperatures
3. Good machinability and surface finish
   • Cuts cleanly, allowing tight-tolerance bores and sealing surfaces
   • Polishes well; suitable for anodic-looking decorative finishes using painting or powder coating
4. Cost-effective material
   • Uses common alloying elements and well-established process windows
   • Foundries worldwide are familiar with EN AC-46000, so sourcing is easier

For OEMs and tier-1 suppliers, this combination reduces both tooling risk and production scrap, especially on large-volume programs.

What are the limitations of AlSi9Cu3 cast aluminum?

No alloy is perfect. Before locking in EN AC-46000, keep these limitations in mind:

1. Low ductility
   • Typical elongation is around 1–3 %.
   • Parts exposed to strong impact or large plastic deformation may need a tougher alloy.
2. Moderate fatigue strength
   • Copper-rich microstructure provides strength but can reduce long-term fatigue performance, especially when casting defects (porosity, inclusions) are present.
   • Critical fatigue parts may require strict process control and NDT.
3. Poor inherent corrosion resistance
   • Corrosion resistance in marine or aggressive environments is limited.
   • Protective coatings (powder coat, paint, e-coat, anodize-look coating) are strongly recommended for outdoor or salt-spray conditions.
4. Not suitable for structural welding
   • High-pressure die-cast AlSi9Cu3 is generally not weld friendly due to porosity, oxide skin, and Cu content.
   • If welding is essential, alternative alloys or localized inserts should be considered.
5. Anodizing limitations
   • The alloy does not anodize to a uniform decorative finish.
   • Use painting, powder coating, or chromate-free conversion coatings instead.

Knowing these trade-offs helps you decide whether AlSi9Cu3 is “good enough” or if your design calls for another alloy.

How does AlSi9Cu3 compare to A380 and other die-casting alloys?

A simplified comparison (typical trends, not exact values):

Feature / Alloy	AlSi9Cu3 (EN AC-46000)	A380 (AlSi8Cu3)	AlSi10Mg / EN AC-43000
Casting process	HPDC	HPDC	HPDC / gravity
Typical strength	High-moderate	High-moderate	Moderate
Ductility	Low	Low-moderate	Higher (with heat treat)
Thermal conductivity	Moderate	Moderate	Slightly higher
Corrosion resistance	Moderate-low	Moderate	Better
Weldability	Poor	Poor	Better (in some tempers)
Best for	Housings, brackets, engine & gearbox components	General automotive HPDC	Parts needing higher ductility or weldability

In many projects, AlSi9Cu3 and A380 are interchangeable with minor adjustments, but EN AC-46000’s tighter European specification can be advantageous for:

• PPAP & documentation with OEMs following EN standards
• Consistent mechanical properties when sourcing across different foundries

If weldability or high ductility is critical, AlSi10Mg or other Mg-modified alloys may be a better choice.

Design tips: wall thickness, heat treatment & quality control

To get the best performance from AlSi9Cu3 die-cast parts:

1. Wall thickness & ribs
   • Aim for uniform wall thickness where possible to reduce porosity and hot spots.
   • Use ribs and fillets rather than very thick sections to achieve stiffness.
   • Avoid sharp transitions from thin to very thick walls.
2. Gating and cooling
   • Proper gate location and overflow design reduce porosity and shrinkage defects.
   • Controlled cooling reduces residual stresses and risk of heat checking in the die.
3. Heat treatment
   • Many AlSi9Cu3 parts are used as-cast or with simple artificial aging.
   • Aggressive solution-treat/quench cycles are rarely applied to HPDC AlSi9Cu3 because of porosity and dimensional stability.
4. Surface protection
   • Plan for painting, powder coating, or e-coat if parts will see outdoor or corrosive environments.
   • For sealing surfaces, specify machined flatness, Ra, and coating thickness control.
5. Quality control
   • For safety-critical parts, consider X-ray, CT, or ultrasonic inspection to monitor internal porosity.
   • Request material certificates (EN 1706, EN AC-46000) with chemical composition and representative mechanical test data.

Need an AlSi9Cu3 die-casting supplier? Work with Yongzhu Casting

If you’re planning a project with AlSi9Cu3 / EN AC-46000, the foundry’s process control is just as important as the alloy itself.

At Yongzhu Casting, we:

• Focus on aluminum and zinc high-pressure die casting for demanding OEM and industrial customers.
• Use large-tonnage die-casting machines suited to complex housings and structural parts.
• Support you from alloy selection and DFM through to tooling, mass production, and post-machining.
• Can recommend whether AlSi9Cu3 is the right alloy for your part, or if another grade (e.g. AlSi10Mg, AlSi9Cu3(Fe) variants) would better fit your performance and cost targets.

If you’d like to review a drawing, compare alloys or discuss EN AC-46000 casting feasibility, you’re welcome to send us your 3D models and requirements.