AlSi10Mg as-built
STRONGESTPrinted, stress-relieved and support-dressed. The maximum strength route: 330–400 MPa with low elongation. Correct for brackets and structural parts where the load path is understood.
330–400 MPaStructuralLow elongation
MATERIAL · ALUMINIUM
Aluminium AlSi10Mg — Light, and Able to Move Heat
AlSi10Mg is the standard aluminium for laser powder-bed printing: a third of the weight of steel, tensile strength in the 330–400 MPa range as printed, and thermal conductivity high enough to make it a genuine heat-sink material. It machines easily, anodises, and takes a load far better than its density suggests.
2.67 g/cm³Density
330–400 MPaTensile strength
~150 W/m·KThermal conductivity
≥99.5 %Printed density
OVERVIEW
What AlSi10Mg actually is
AlSi10Mg is a casting-grade aluminium alloy with roughly 10 % silicon and a small amount of magnesium. It was designed for die casting, and it transferred to laser powder-bed printing precisely because it behaves well when it is melted and cooled fast: the silicon gives the alloy a wide solidification range and good fluidity, which means a stable melt pool and a dense part without the cracking that plagues high-strength wrought alloys like 7075 in a printer.
The as-printed properties are better than the same alloy in a casting. Rapid solidification produces a very fine cellular silicon network inside the aluminium matrix, and that structure is what gives printed AlSi10Mg its 330–400 MPa tensile strength — well above the same alloy cast. Heat treatment then changes the balance: it relieves stress and coarsens the silicon, which raises ductility and thermal conductivity while dropping strength somewhat. Which you want depends on whether the part is structural or thermal.
The reason to reach for aluminium is almost always mass, heat or both. At 2.67 g/cm³ it is 40 % lighter than titanium and 66 % lighter than steel, and its thermal conductivity — around 150 W/m·K once heat treated — is an order of magnitude above 316L and twenty times titanium. That combination is why aluminium is the default for drone structures, electronics housings, cold plates and heat sinks, and why topology-optimised aluminium brackets are the classic SLM showcase part. The limitations are equally clear: it is the softest metal we print, it has a modest service temperature, and its thermal expansion is high.
PROPERTIES
Mechanical, Thermal & Chemical Data
Typical values for AlSi10Mg printed by SLM. Note the trade-off between the as-built and heat-treated conditions: strength and ductility move in opposite directions and thermal conductivity improves with the heat treatment.
Density2.67 g/cm³ — roughly a third of steel, 40 % lighter than titanium
Tensile strength330 – 400 MPa as-built. Drops toward 200–300 MPa after a full T6-style heat treatment, in exchange for ductility.
Yield strength (0.2 % offset)~230 – 280 MPa as-built
Elongation at break~5 – 8 % as-built; rises to 10–15 % after heat treatment
Young’s modulus~70 GPa — about a third of steel. Stiffness is aluminium’s weak point, not strength.
Hardness~110 – 130 HV as-built
Relative density≥ 99.5 %
Service temperature~170 °C continuous as-built. Above that the fine silicon structure coarsens and strength falls away quickly.
Thermal conductivity~120 – 150 W/m·K depending on heat treatment — an order of magnitude above 316L
CTE~23 × 10⁻⁶ /K — the highest of our metals. Design in allowance on long parts and mixed-material assemblies.
Corrosion resistanceModerate. Forms a protective oxide naturally but pitting is possible in chlorides. Anodising is the normal answer for anything exposed.
MachinabilityExcellent — the easiest of our metals to machine after printing.
WeldabilityGood, but weld strength in the heat-affected zone drops. Prefer mechanical joints or inserts on anything structural.
AnodisingYes. Note that the silicon content makes the coating darker and less transparent than on pure aluminium — expect a grey or charcoal natural finish rather than bright silver.
As-built surfaceRa 6 – 12 µm matte granular; machining brings it to Ra 1.6 µm or better.
GRADES & VARIANTS
AlSi10Mg Conditions & Finishes
The condition changes this alloy more than most. Pick by whether the part is loaded or whether it moves heat.
AlSi10Mg heat treated
DUCTILEA T6-style solution and ageing cycle coarsens the silicon network. Strength drops, ductility and thermal conductivity rise. The right choice for anything that sees impact or has to move heat.
DuctileConductiveImpact tolerant
Machined interfaces
TIGHT FITBores, bearing seats, sealing faces and threads cut from the printed blank. Aluminium machines beautifully, so this is cheap insurance on any functional interface.
Bearing seatsThreadsFlatness
Bead-blasted
COSMETICA uniform matte grey that hides layer texture and gives an even base for paint or anodising. The default cosmetic finish.
Uniform mattePaint base
Anodised
CORROSION & WEARType II for colour and protection, Type III hard anodising for wear resistance on sliding surfaces. Expect a darker natural tone than on pure aluminium because of the silicon content.
CorrosionWearColour
Polished & tumbled
FLOWPolishing or mass finishing to lower the roughness. Used on flow paths, air ducts and visible surfaces where the matte texture is not acceptable.
Flow pathsLow Ra
Aluminium powder is available in bulk for your own machines — see powder supply. Higher-strength wrought alloys such as 7075 are not generally printable and we will say so rather than experiment on your part.
FINISHING
Finishing AlSi10Mg
Aluminium is the most machinable and most finishable metal we print. Most of the work goes into protecting it, not shaping it.
Support removal & dressing
Supports come off the plate and are dressed by hand. Aluminium dresses quickly, so witness marks on downward faces are less of a cost problem here than on titanium.
Stress relief / heat treatment
A governed thermal cycle either relaxes residual stress only, or fully coarsens the silicon for ductility and conductivity. Tell us which behaviour you need so we quote the right one.
CNC machining
Mating faces, bores, bearing seats and threads cut from printed stock. Fast and inexpensive in aluminium, and the only way to hold a real tolerance on a functional interface.
Wire EDM
Clean removal from the base plate with a flat witness face, and useful for thin sections that would deflect under a cutter.
Bead blasting
A uniform matte surface that hides layer texture and gives paint and adhesive a key.
Anodising
Type II for colour and general protection, Type III hard anodising for wear surfaces. Natural anodised AlSi10Mg reads grey to charcoal because of the silicon.
Polishing & tumbling
Progressive polishing for visible surfaces; mass finishing for small parts in quantity where hand work would dominate the price.
Chromate conversion
A thin conductive conversion coating used when the part must stay electrically conductive but still needs corrosion protection — anodising is an insulator.
WHERE IT FITS
Where AlSi10Mg Is the Right Answer
Aluminium wins on mass, heat and machinability, and it loses on stiffness and service temperature. These are the applications where the trade lands the right way.
Strengths
- Lightest metal we print — 2.67 g/cm³, a third of steel
- Thermal conductivity an order of magnitude above 316L, so it is a real heat-sink material
- Machines better than any other metal we run, which makes tight interfaces cheap to achieve
- Anodises for colour, corrosion protection and wear resistance
- Dissipates heat well during printing, so thin walls and fine features build cleanly
- Costs far less per part than titanium or copper
- The standard material for drone, robotics and automotive weight reduction
Limits to know
- Low stiffness (~70 GPa): a part can be strong enough and still deflect too much
- Modest service temperature (~170 °C) — the fine printed structure coarsens above it
- Softest metal we print; wear surfaces need anodising or an insert
- Pitting risk in chlorides unless anodised or conversion coated
- Highest thermal expansion of our metals, which complicates mixed-material assemblies
- Heat treatment trades strength for ductility — you cannot have both at once
- Anodising on silicon-bearing aluminium never looks like bright clear anodising on pure aluminium
Heat sinks and cold plates
Pin fins, skived geometries and conformal channels that follow the heat source rather than the tool path. This is where aluminium is not just adequate but optimal.
RF, waveguide and antenna housings
Complex internal cavities and lightweight structures with the electrical conductivity needed for microwave work. Expect to machine the mating faces and finish the surface.
Drone and UAV frames
Weight-optimised structural parts with integrated cable routing, printed in a material that keeps the airborne mass where it belongs: low.
Automotive and motorsport brackets
Topology-optimised brackets, mounts and housings that carry a known load at a fraction of the machined mass, produced outside the tooling cycle.
Robot end-effectors and grippers
Low moving mass is what lets a robot move faster and use a smaller actuator, so printed aluminium arms and gripper bodies routinely beat steel ones on cycle time.
Electronics enclosures and chassis
Housings that hold the board, mount the connectors and act as the heat sink at the same time, in one printed piece instead of an assembly.
Consumer product internals
Invisible internal structures, brackets, and battery or motor mounts where weight and heat both matter and the part is never seen.
Prototyping before casting
Print the actual AlSi10Mg part, test it, and then take the same geometry to die casting — the printed part is a genuine material-level prototype, not a proxy.
COMPARISON
How AlSi10Mg Compares
Aluminium is the light, thermally conductive, easily machined option. Here is what you give up against its neighbours.
| Material | Process | Density | Strength | Heat | Pick it when |
|---|---|---|---|---|---|
| Ti-6Al-4V | SLM | 4.43 g/cm³ | 900–1100 MPa | ~400 °C | Strength per gram, or biocompatibility |
| 316L stainless | SLM | 7.9 g/cm³ | 480–620 MPa | ~400 °C | Corrosion resistance and ductility |
| AlSi10Mg | SLM | 2.67 g/cm³ | 330–400 MPa | ~170 °C | Light, thermally conductive, easy to machine |
| Copper & Cu alloys | SLM | 8.9 g/cm³ | 210–400 MPa | ~200 °C | Electrical or thermal conductivity |
| PA12 nylon | SLS | 1.01 g/cm³ | 48–50 MPa | ~120 °C | Tough, complex geometry, no supports |
| Photopolymer resins | SLA | ~1.1–1.2 g/cm³ | 40–70 MPa | ~80 °C | Detail, smoothness, transparency |
If the part has to be stiff as well as light, neither aluminium nor titanium will be satisfying on its own — stiffness scales with modulus and geometry, so the answer is usually a thicker or better-shaped aluminium part, or accepting steel. Send us the deflection limit and we will tell you which one closes it.
FAQ
AlSi10Mg — Common Questions
How strong is printed AlSi10Mg compared with cast aluminium?
Stronger, typically. Rapid solidification produces a fine cellular silicon network that raises tensile strength to 330–400 MPa, above the same alloy in a conventional casting. The advantage is lost if the part is then heat treated for ductility — that is a deliberate trade, not a defect.
Can aluminium parts be welded?
They can, but printed AlSi10Mg joints lose strength in the heat-affected zone. For anything structural we would rather design a bolted joint, a press-fit insert or a machined interface than rely on a weld. Tell us if welding is mandatory and we will say honestly how much margin you have.
Why did my heat-treated part come back weaker?
Because heat treatment coarsens the fine silicon structure that gives the as-built material its strength. What you gain is ductility and thermal conductivity, which is usually what a thermal or impact-loaded part actually needs. If the part is a structural bracket, order it as-built.
Is anodised AlSi10Mg the same as anodised aluminium?
No, and it surprises people. The 10 % silicon content interferes with the anodic layer, so a natural anodised finish on AlSi10Mg comes out grey to charcoal rather than bright silver, and clear anodising is not achievable. Black anodising works well. If the cosmetic result matters, ask for a sample coupon first.
What is the biggest aluminium part you can print?
The machine envelope sets a single-piece limit, and beyond it we print sections and join them. Aluminium is weldable but loses strength at the joint, so for large structural parts we would usually rather redesign into a bolted assembly with machined interfaces. Send the drawing and we will advise.
Aluminium or nylon for a functional prototype?
Aluminium if the prototype has to prove a thermal, electrical or stiffness behaviour, or if it will be used as a real part. Nylon if you are checking form, fit and function and the part does not get hot. Nylon is cheaper and faster; aluminium tells you the truth about heat and stiffness.
Related reading
GET STARTED
Light Parts, and Parts That Move Heat
Send the drawing with the load and, if it applies, the thermal duty. We will tell you whether as-built or heat-treated AlSi10Mg suits it and what the finishing route should be.
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