An engineer sends a European drawing marked "EN AC-AlSi10Mg" to an Asian supplier and gets a quote back for ADC12. That swap is wrong, and catching it early saves a qualification loop. AlSi10Mg aluminum is a low-copper, heat-treatable casting alloy that sits between the high-volume die casting workhorses and the wrought structural grades, with one unusual trait: it is also the default alloy of metal 3D printing. This guide covers its composition, properties, casting and printing behavior, equivalents, and when to specify it.
What Is AlSi10Mg Aluminum?
AlSi10Mg is an aluminum-silicon-magnesium casting alloy containing roughly 9–11% silicon and 0.2–0.65% magnesium, standardized in Europe as EN AC-43000 and EN AC-43400 under EN 1706. The silicon provides fluidity and low shrinkage, while the magnesium enables precipitation hardening for higher strength and fatigue resistance. It serves structural castings and is the most common aluminum powder alloy in laser powder bed fusion.
On drawings it appears as AlSi10Mg, EN AC-AlSi10Mg, or EN AC-43000, supplied as-cast, stress-relieved, or T6 heat treated, then machined and finished to final requirements. Because copper is nearly absent, it outperforms Cu-rich grades such as A380 and AlSi9Cu3 on corrosion resistance, weldability, and fatigue life, which is exactly why engineers specify it for load-bearing parts.
Chemical Composition and EN Grades
The alloy is defined by high silicon for castability, a deliberate magnesium addition for hardening, and tight limits on copper and iron. EN AC-43000 covers general casting routes; EN AC-43400 holds tighter impurity limits for pressure die casting. Powder for additive manufacturing uses the same nominal chemistry with even tighter trace-element control. Always confirm limits against EN 1706 or the customer material specification.
| Element | Typical Limit (wt%) | What It Does |
|---|---|---|
| Silicon (Si) | 9.0–11.0 | Fluidity, low shrinkage, wear resistance |
| Magnesium (Mg) | 0.2–0.65 | Precipitation hardening (Mg2Si), strength and fatigue |
| Iron (Fe) | ≤0.55 | Controlled low for ductility, fatigue, and weldability |
| Copper (Cu) | ≤0.05 | Kept minimal to protect corrosion resistance |
| Manganese (Mn) | ≤0.55 | Modifies iron phases, reduces brittleness |
| Zinc (Zn) | ≤0.10 | Impurity control |
| Titanium (Ti) | ≤0.15 | Grain refinement |
| Aluminum (Al) | Balance | Base metal |
The low copper ceiling deserves attention. Copper is the cheapest way to add strength to a casting alloy, and removing it is what separates this grade from the A380 family. The trade shows up as better corrosion behavior in chloride environments, reliable weld repair, and a genuine response to T6 heat treatment through Mg2Si precipitation.
Mechanical and Physical Properties
Cast AlSi10Mg typically delivers 240–320 MPa tensile strength and 150–220 MPa yield strength, with density around 2.65–2.68 g/cm³. Elongation varies widely with process: 1–4% in high-pressure die casting, and up to about 10% in well-fed gravity castings or heat-treated printed parts. Thermal conductivity of 130–180 W/m·K suits components that must move heat, and hardness runs 65–90 HB depending on temper.
| Property | Typical Value | Notes |
|---|---|---|
| Density | 2.65–2.68 g/cm³ | Among the lightest structural casting alloys |
| Melting range | approx. 570–610 °C | Near-eutectic Al-Si behavior |
| Tensile strength | 240–320 MPa (cast) | Up to 400–460 MPa for optimized 3D printed parts |
| Yield strength (Rp0.2) | 150–220 MPa (cast) | Depends on process and temper |
| Elongation | 1–4% (HPDC), up to ~10% (gravity/AM, treated) | Process and section dependent |
| Hardness | 65–90 HB | As-cast to T6 range |
| Young's modulus | ~71 GPa | Typical for Al-Si alloys |
| Thermal conductivity | 130–180 W/m·K | Suits heat-dissipating parts |
| Electrical conductivity | ~25–30% IACS | Better than Cu-rich casting alloys |
| Thermal expansion | 20–23 µm/m·K | 0–100 °C range |
Treat these as screening values, not guaranteed minima. Wall thickness, porosity level, and temper move real parts up or down the range, so critical features should be confirmed with tensile bars cast alongside the production run.
Casting vs 3D Printing: One Alloy, Two Routes
AlSi10Mg is unusual because the same chemistry dominates both pressure die casting and selective laser melting. Casting wins on piece price once tooling exists and suits medium to high volumes. Printing wins on geometry freedom, internal channels, and part consolidation, but powder cost and machine time keep it economical only for low volumes or high-value parts. A practical path many buyers use: prototype in printed AlSi10Mg, freeze the geometry, then convert to cast AlSi10Mg for volume production without re-qualifying the material.
Process behavior differs enough to matter. Printed parts show higher as-built strength but carry anisotropy and residual stress, so stress relief or solution treatment is standard. Cast parts depend on feeding and porosity control, and high-pressure die castings are generally kept as-cast or lightly treated because trapped gas can blister during full solution treatment. If a drawing calls for T6 on a die casting, raise it at the DFM stage rather than discovering it at PPAP. For background on temper cycles, see our guide to aluminum casting heat treatment.
AlSi10Mg vs A360, A380, and 6061
A360 is the closest ASTM analog, with nearly the same chemistry and slightly more magnesium; US drawings often use it where European ones say AlSi10Mg. A380 casts more easily and costs less, but its 3–4% copper sacrifices the corrosion resistance and weldability that define AlSi10Mg. Wrought 6061-T6 offers higher ductility, yet needs machining from solid stock, which costs more than near-net-shape casting at volume. The manganese-modified variant AlSi10MnMg exists specifically for structural die castings, where manganese reduces die soldering and lifts ductility.
| Alloy | Character | Pick It When |
|---|---|---|
| AlSi10Mg (EN AC-43000) | Low-Cu structural casting alloy, heat treatable, weldable | Load-bearing or corrosion-sensitive castings; AM-to-casting programs |
| A360 (closest ASTM analog) | Very similar chemistry, slightly higher Mg | US-spec drawings calling for the same performance class |
| A380 / AlSi9Cu3 | Higher Cu, best castability and lowest cost | High-volume housings where corrosion and welding are secondary |
| 6061-T6 (wrought) | Higher ductility, extrusion/forging route | Machined-from-solid parts, or when casting is not an option |
For gravity and low-pressure work, A356 aluminum is the other low-iron structural option engineers usually weigh against this family, trading a little silicon for excellent elongation in T6 condition.
Typical Applications
The alloy shows up wherever castings carry real loads. Automotive and commercial vehicle programs use it for chassis and suspension brackets, steering housings, and structural cross-members. Aerospace uses it for brackets, actuator housings, and topology-optimized printed fittings. Industrial and robotics builders choose it for gearbox housings and robot arm joints, and its thermal conductivity puts it in heat sinks, cooling plates, and housings near motors. In additive manufacturing it is the default powder for lattice structures, conformal-cooled inserts, and consolidated assemblies.
Design and Sourcing Notes
Keep walls uniform, add stiffness with ribs instead of thickness, and give internal corners at least a small fillet so the melt feeds without turbulence. Decide the temper early, because as-cast, stress-relieved, and T6 conditions imply different tooling and inspection plans. Concentrate tight tolerances on machined pads and leave the rest as-cast. On surface finishing, the alloy accepts powder coating and conversion coatings readily, and anodizes more cleanly than high-silicon or copper-rich grades, though decorative Class I finishes still favor wrought material.
When you brief suppliers, share the load cases and annual volume with the drawing. Alloy choice, casting route, and heat treatment are one decision, and a foundry that runs simulation before cutting steel will catch filling risks while changes are still cheap. We cast aluminum across 20 cold chamber machines from 160T to 1650T, with every ingot lot verified by fluorescence spectrometer and every new mold validated by JSCAST flow simulation, under an IATF 16949 quality system. If you are scoping an aluminum die casting program in this alloy, send the part file and we will return a DFM review with a process recommendation.
The short version: specify AlSi10Mg aluminum when the part is structural, corrosion-sensitive, weld-repairable, or moving between printing and casting. Share drawings, volumes, and load requirements with our engineering team for a free alloy and process review.
