AlSi12
metalaluminium — hypoeutectic/eutectic Al-Si
AlSi12 AMAl-Si12A413 AM equivalentEN AC-44100 AMEOS AlSi12Scalmalloy alternative — castability grade
Composition — EN AC-44100 / ASTM A413 equivalent — Al-Si12 (12 wt% Si nominal)
| Element | Min % | Max % | Notes |
|---|---|---|---|
| Al | — | — | balance — aluminium matrix |
| Si | 11.00 | 13.500 | 12.6 wt% is the eutectic composition; Si content drives fluidity and sets thermal conductivity |
| Fe | — | 0.550 | Iron impurity; forms Al₃Fe intermetallics that can reduce ductility |
| Cu | — | 0.050 | Minimal copper content — not a precipitation-hardening alloy |
| Mg | — | 0.100 | Trace Mg only — insufficient for Mg₂Si precipitation hardening (contrast with AlSi10Mg which has ~0.3% Mg) |
| Mn | — | 0.450 | Manganese for minor strength contribution |
| Zn | — | 0.100 | Zinc trace impurity |
Mechanical & thermal properties — 2 conditions
| Property | LPBF as-built (XY) | LPBF stress-relieved 300°C/2h (XY) |
|---|---|---|
| Elastic modulus | 70–76 GPa | 72 GPa |
| Yield strength (0.2%) | 180–230 MPa | 130–175 MPa |
| Ultimate tensile strength | 280–350 MPa | 220–280 MPa |
| Elongation at break | 3.0–8.0 % | 5.0–12.0 % |
| Hardness (HV) | 95–120 HV | 75–95 HV |
| Density | 2.67 g/cm³ | 2.67 g/cm³ |
| Thermal conductivity | 120.0–145.0 W/m·K | 150.0–170.0 W/m·K |
| CTE | 20.5 µm/m·K | — |
Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.
Engineering considerations
- Heat treatment decision: If maximum strength is required, specify as-built and DO NOT stress relieve. If dimensional stability, ductility, or thermal conductivity is the priority, specify 300°C/2h stress relief. A full anneal (>350°C) is rarely warranted — it reduces strength below die-cast equivalents.
- Thermal conductivity optimisation: Stress-relieved AlSi12 (~160 W/m·K) outperforms stress-relieved AlSi10Mg (~150 W/m·K) due to higher Si content. For pure thermal management, AlSi12 is the better choice.
- Porosity management: AlSi12's eutectic composition makes it one of the most process-tolerant Al alloys for LPBF. Still verify relative density >99% for pressure-tight components; hydrogen porosity from atmospheric moisture can occur if powder is not properly dried.
- Comparison with AlSi10Mg: Choose AlSi12 when (1) castability/processability is paramount, (2) no heat treatment is planned, (3) thermal conductivity trumps strength. Choose AlSi10Mg when (1) highest as-built or T6-equivalent strength is needed, (2) the application involves sustained loads or fatigue.
- Build orientation: Mechanical properties are anisotropic (Z-direction typically ~15–20% weaker than XY). Orient critical load paths in XY; verify Z-direction data for vertical features.
- Surface quality: AlSi12 achieves good as-built surface roughness (Ra ~8–12 µm on vertical faces). For sealing surfaces or sliding fits, machining or abrasive finishing to Ra <3.2 µm is recommended.
Advantages
- Eutectic composition gives near-zero solidification shrinkage — excellent dimensional accuracy and low porosity tendency vs hypoeutectic Al alloys
- Best LPBF processability of the common Al-Si alloys — stable melt pool, low hot-cracking tendency
- Higher thermal conductivity than AlSi10Mg in stress-relieved condition (~160 vs ~150 W/m·K) — preferred for pure thermal management applications
- Good surface finish capability — suitable for complex thin-wall geometries
- Well-established material for die-casting — AM AlSi12 can directly replace cast A413/EN AC-44100 components with design consolidation
- No Mg requirement means less sensitivity to moisture-induced porosity vs AlSi10Mg
Limitations
- Not precipitation-hardenable (no Mg for Mg₂Si precipitates) — as-built condition is peak strength; heat treatment only reduces strength
- Lower strength than AlSi10Mg (~310 vs ~400–450 MPa UTS as-built) — not suitable where high specific strength is needed
- Limited ductility in as-built condition (~5% elongation) — stress relief is recommended for any application involving cyclic loads or impact
- Not a structural aerospace alloy — AlSi10Mg, Scalmalloy, or Ti-6Al-4V are preferred for aerospace structural applications
- Moderate machinability — silicon particles cause tool wear; use carbide tooling with high cutting speeds
- Limited post-AM heat treatment options vs AlSi10Mg (no T6 equivalent)
Typical applications
Automotive thermal management components (coolant manifolds, heat exchanger headers)Lighting brackets and housings requiring thin walls and good surface finishDie-cast replacement parts requiring near-net-shape geometry with AM complexityEnclosures and housings for electronics where thermal management is neededPrototype casting patterns and production-intent near-net-shape insertsLightweight structural brackets where thermal conductivity is secondary
Industries
automotiveindustrialelectronicsconsumer
Compatible AM processes (2)
Other metal materials
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Related calculators
LPBF Porosity PredictorPredict lack-of-fusion and keyhole porosity from laser parameters. Maps VED and normalised enthalpy to relative density and flags dangerous regimes.Powder Characterisation TrackerScore a powder batch against key qualification metrics — particle size distribution, flowability, apparent/tap density, moisture, and oxygen content.Melt PoolLPBF / DED melt pool depth, width, and cooling rate from the Rosenthal moving heat source solution. Absorptivity, thermal diffusivity, and solidification velocity.Laser ParamsDerive LPBF process parameters from target VED and melt-pool stability constraints. Power–speed–hatch–layer sensitivity matrix with keyholing and balling risk zones.DistortionEstimate residual stress and distortion risk index (σ/σ_y) for LPBF and DED builds. Mercelis-Kruth model with preheat sensitivity table.HT AdvisorStandard stress-relief, solution, and aging cycles for AM metals (Ti-6Al-4V, IN718, 17-4PH, AlSi10Mg, 316L, CuCrZr) per AMS, ASTM F3301, and AMS 5664.
Last reviewed: 2026-05-15 · v1 · Sources: rosenthal-2014-alsi12, prashanth-2017-alsi12, siddique-2015-alsi12
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