AlSi7Mg Aluminium Alloy

metal

hypoeutectic Al-Si-Mg precipitation-hardenable aluminium alloy

AlSi7Mg0.6EN AC-42100EN 1706 AC-AlSi7MgA357.0 (near-equivalent)UNS A13570AlSi7Mg 0.6EOS Aluminium AlSi7Mg

AlSi7Mg Aluminium Alloy 3D printed component

Density

2.67 g/cm³

YS (LPBF + As-built (XY))

190–235 MPa

UTS (LPBF + As-built (XY))

300–350 MPa

Elongation (LPBF + As-built (XY))

6.0–11.0 %

Elastic modulus

71 GPa

Thermal conductivity

145.0–170.0 W/m·K

Composition — EN AC-42100 / EN 1706 (near A357.0)

Element	Min %	Max %	Notes
Al	bal.		balance
Si	6.50	7.500	Primary eutectic-forming element. Lower Si than AlSi10Mg → finer, less-continuous eutectic network → better ductility
Mg	0.45	0.700	Forms Mg₂Si precipitates during T6 aging — primary strengthening mechanism
Fe	—	0.200	Iron limit critical in AM: Fe-rich β-needles (Al₅FeSi) are crack initiation sites. AM powder spec typically ≤0.15% Fe
Mn	—	0.100	Mn partially offsets Fe-needle embrittlement by converting β-Al₅FeSi to α-Al₁₅(Fe,Mn)₃Si₂ script phase

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Mechanical & thermal properties — 3 conditions

Property	LPBF + As-built (XY)	LPBF + T6 (XY)	LPBF + As-built (Z — build direction)
Elastic modulus	71 GPa	71 GPa	—
Yield strength (0.2%)	190–235 MPa	245–290 MPa	175–215 MPa
Ultimate tensile strength	300–350 MPa	315–375 MPa	275–330 MPa
Elongation at break	6.0–11.0 %	8.0–14.0 %	5.0–9.0 %
Hardness (HV)	85–110 HV10	95–120 HV10	—
Density	2.67 g/cm³	2.67 g/cm³	—
Thermal conductivity	145.0–170.0 W/m·K	160.0–180.0 W/m·K	—
CTE	21.5–23.5 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

T6 cycle optimisation: standard T6 for LPBF AlSi7Mg is 530°C/5h/WQ + 160°C/6h. Over-aging (>175°C or >8h) precipitates coarse Mg₂Si and reduces yield strength below 230 MPa. Under-aging leaves unsatisfactory Mg₂Si distribution and poor fatigue life.
Stress relief before T6: add a stress relief step (300°C/2h/air cool) before solution treatment for large or complex parts. Reduces distortion during solution treatment quench by releasing as-built residual stresses.
Quench rate sensitivity: water quench is standard for solution treatment. Use polymer quench (PAG solution) for complex parts with thin features — reduces quench distortion while maintaining near-water cooling rate for adequate Mg₂Si dissolution.
Support design: AlSi7Mg supports detach more easily than steel but still require adequate cross-section. Prefer 45° angle grid supports over solid walls. Minimum support contact width: 0.4 mm for reliable detachment without substrate damage.
Powder reuse: AlSi7Mg powder can tolerate 20–30 build cycles with regular sieving and oxygen monitoring. Si partitioning and Mg burn-off occur preferentially in the melt pool — blend at ≥30% virgin powder per cycle. Maximum O content: 0.08%.
Anisotropy management: Z-direction properties are ~7–10% lower as-built. T6 heat treatment substantially reduces anisotropy — T6 Z/XY YS ratio typically improves to 0.95 from 0.93 as-built. For fatigue-critical applications, orient load axis in XY plane and/or HIP + T6.
HIP considerations: HIP (520°C / 100 MPa / 4h) before T6 eliminates internal porosity and substantially improves fatigue performance (+30–60% endurance limit). Specify HIP + T6 for fatigue-critical components (rotating, cyclic loading).
Corrosion: AlSi7Mg offers good general corrosion resistance. Anodise (hard anodise for wear resistance, class 2 for corrosion) after T6 and finish machining. Avoid crevices and dissimilar metal contacts (galvanic risk vs steel fasteners — use titanium or Al rivets).

Advantages

Superior T6 ductility vs AlSi10Mg (11–14% vs 7–8% El) — preferred for damage-tolerant aerospace applications
T6 yield strength comparable to wrought A357-T6 (~265 MPa) with complex LPBF geometry
Lower Si content improves weld and repair compatibility after LPBF
Excellent specific strength: YS/density ~99 MPa·cm³/g in T6 condition
Good thermal conductivity (155–170 W/m·K) for heat-exchanging structures
Low density (2.67 g/cm³) — second lightest commercially used AM metal after magnesium alloys
Anodising quality better than AlSi10Mg (less Si exposure at surface)

Limitations

No dedicated AM product standard (unlike Ti-6Al-4V ASTM F2924 or IN718 ASTM F3056) — qualification requires test-based approach
T6 solution treatment at 530°C requires controlled atmosphere or vacuum furnace — rapid heating and quench critical to dissolve eutectic Si
As-built strength lower than AlSi10Mg — if no T6 is planned, AlSi10Mg is a better as-built choice
Hot cracking susceptibility higher than some AM aluminium alloys (AlSi12, Al-alloys with Sc) — scan strategy and preheating critical
Not weldable with standard MIG/TIG filler without additional filler alloy selection — specify ER4043 or ER4047 filler
Limited commercial powder sources vs AlSi10Mg — fewer second-source options for powder qualification
LPBF support structures in AlSi7Mg are fragile due to brittle, Si-rich HAZ — design for easier support removal

Typical applications

Aerospace structural brackets, seat rails, and interior fittings requiring >8% elongationAutomotive suspension components and lightweight structural nodesThin-walled heat exchangers and thermal management structuresRacing/motorsport uprights and corner componentsUnmanned aerial vehicle (UAV) airframes and structural ribsSatellite and spacecraft brackets requiring high specific strengthIndustrial fixtures requiring weld/repair capability after LPBF

Standards & certifications

ASTM-B179established

Aluminium alloys in ingot form for foundry use — composition reference for A357.0 (near-equivalent to AlSi7Mg0.6)

aerospaceautomotiveindustrial

ASTM-E8established

Uniaxial tensile testing method for mechanical property acceptance testing of AM specimens

aerospaceautomotiveindustrial

ASTM-E92established

Vickers hardness testing for condition verification

aerospaceindustrial

AlSi7Mg Aluminium Alloy

Composition — EN AC-42100 / EN 1706 (near A357.0)

Mechanical & thermal properties — 3 conditions

Engineering considerations

Advantages

Limitations

Typical applications

Industries

Standards & certifications

Compatible AM processes (1)

Other metal materials

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