AlSi7Mg (A356)
The premier aluminum casting alloy, with excellent fluidity and castability for complex and safety-critical parts.
The A356/AlSi7Mg family is the most important aluminum casting alloy in the world. Its silicon content (6.5–7.5%) provides excellent fluidity for complex mold filling. The A356.2 version has ultra-low iron content (≤0.12%), achieving superior ductility and fatigue life — making it preferred for aluminum wheels and structural automotive components. We manufacture this alloy from both primary and secondary aluminum base depending on customer specifications.
International Nomenclature
| Standard | Designation |
|---|---|
| AA (USA) | A356.0 / A356.2 |
| EN (Europa) | EN AC-42100 · AlSi7Mg0.3 |
| DIN (Alemania) | G-AlSi7Mg / 3.2371 |
| ISO | AlSi7Mg |
| JIS (Japón) | AC4C |
| NF (Francia) | A-S7G03 |
| UNI (Italia) | G-AlSi7Mg |
Chemical Composition
| Element | Symbol | Percentage |
|---|---|---|
| Aluminum | Al | Balance |
| Silicon | Si | 6.50–7.50% |
| Magnesium | Mg | 0.25–0.45% |
| Iron | Fe | ≤0.20% (A356) · ≤0.12% (A356.2) |
| Copper | Cu | ≤0.20% |
| Manganese | Mn | ≤0.10% |
| Zinc | Zn | ≤0.10% |
| Titanium | Ti | ≤0.20% |
Physical Properties
| Property | Value |
|---|---|
| Density | 2.67 g/cm³ |
| Melting Range | 557–615 °C |
| Thermal Conductivity | 149–155 W/m·K |
| Electrical Conductivity | 33–40% IACS |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength (UTS) | ~310 MPa (T6) |
| Yield Strength | ~230 MPa (T6) |
| Elongation | 3–10% (A356.2 T6: 6–10%) |
| Hardness | ~75 HB |
Key Characteristics
- Premier aluminum casting alloy worldwide
- High silicon content (6.5–7.5%) provides excellent fluidity for complex molds
- A356.2 with ultra-low iron (≤0.12%) for safety-critical applications like wheels
- Available with primary aluminum base for maximum purity and ductility
- Low shrinkage during solidification reduces internal defects
- Heat-treatable across multiple tempers (F, T5, T6, T61, T71)
Compared to Similar Alloys
AlSi7Mg (A356) vs AlSi7Mg0.6 (A357)
These are sibling Al-Si-Mg alloys with identical silicon (6.5–7.5%), so they share fluidity and castability. The key difference is magnesium: A356 runs 0.25–0.45% while A357 raises it to 0.45–0.60%, which after T6 heat treatment gives A357 ~15% higher mechanical strength, with even tighter iron control.
| Dimension | AlSi7Mg (A356) | AlSi7Mg0.6 (A357) |
|---|---|---|
| Magnesium (key alloying element) | 0.25–0.45% Mg — Si 6.5–7.5%, Cu ≤0.20% | 0.45–0.60% Mg — same Si 6.5–7.5%; optional Be 0.04–0.07% |
| Heat treatment & strength (T6) | T6: UTS ~310 MPa, yield ~230 MPa, ~75 HB. Tempers F/T5/T6/T61/T71 | T6: UTS ~345 MPa, yield ~290 MPa, ~100 HB (~15% higher). Tempers T6/T61 |
| Ductility / elongation (T6) | 3–10%; A356.2 (Fe ≤0.12%) reaches 6–10% | 2–5%; A357.2 (Fe ≤0.09%) reaches 5–8% — more strength, slightly less elongation |
| Iron control / base metal | Fe ≤0.20% (A356) · ≤0.12% (A356.2); primary or secondary base per spec | Fe ≤0.20% (A357) · ≤0.09% (A357.2); manufactured exclusively from primary aluminum base (P0610) |
| Casting process | Excellent fluidity and low shrinkage; permanent mold, sand, gravity. Sr-modifiable | Same castability (identical Si); strontium-modifiable for eutectic refinement |
| Typical application | Aluminum wheels, cylinder heads, suspension, landing gear — the versatile workhorse | Structural nodes, shock towers, subframes, aerospace — top safety-critical strength |
AlSi7Mg (A356): Choose A356 when you need the versatile reference casting alloy with maximum ductility and fatigue life (e.g. A356.2 wheels) and the flexibility of a primary or secondary base.
AlSi7Mg0.6 (A357): Choose A357 when you need ~15% higher strength after T6 for safety-critical structural parts (nodes, subframes, aerospace), accepting the tighter iron control and primary-aluminum base.
A360 (AlSi10Mg) vs AlSi7Mg (A356)
Both are low-copper Al-Si-Mg alloys, but they differ in process and silicon: A360 is the high-pressure die-casting (HPDC) version with ~10% Si and a higher tolerated iron level (≤1.30% A360 / ≤2.0% 360), delivered as-cast (F temper); AlSi7Mg (A356) has less silicon (6.5–7.5%), much lower iron (≤0.20%, or ≤0.12% in A356.2) and is heat-treatable (T5/T6/T61/T71) for gravity, permanent-mold, and sand casting. In short: A360 = high-volume as-cast die parts; A356 = ductile, heat-treatable, safety-critical structural castings.
| Dimension | A360 (AlSi10Mg) | AlSi7Mg (A356) |
|---|---|---|
| Key composition (Si / Mg / Cu / Fe) | Si 9.0–10.0% · Mg 0.40–0.60% · Cu ≤0.60% · Fe ≤1.30% (A360) / ≤2.0% (360) | Si 6.5–7.5% · Mg 0.25–0.45% · Cu ≤0.20% · Fe ≤0.20% (≤0.12% A356.2) |
| Casting process | High-pressure die casting (HPDC), high volume | Gravity, permanent-mold, and sand casting |
| Heat treatment & strength | As-cast (F): UTS ~320 MPa, yield ~165 MPa | Heat-treatable (F/T5/T6/T61/T71); T6: UTS ~310 MPa, yield ~230 MPa |
| Ductility (elongation) | 2.5–5% | 3–10% (A356.2 T6: 6–10%, ~20% tougher) |
| Fluidity / mold filling | Higher (more Si, near eutectic) — thin walls and pressure tightness | Excellent castability and low shrinkage, suited to complex molds |
| Thermal conductivity | 130 W/m·K (~30% IACS) | 149–155 W/m·K (33–40% IACS) |
| Typical application | Transmission housings, pressure-tight valve bodies/manifolds, heat-dissipating electronic enclosures | Aluminum wheels, suspension, and safety-critical structural/aerospace parts |
A360 (AlSi10Mg): Choose A360 when you produce high-volume thin-wall die-cast (HPDC) parts that need excellent fluidity, pressure tightness, and die-soldering resistance, and you can use them as-cast (F temper) with tolerance for higher iron.
AlSi7Mg (A356): Choose AlSi7Mg (A356) when you need safety-critical structural parts such as wheels or suspension, gravity/permanent-mold cast, with maximum ductility and fatigue life from low iron (A356.2 ≤0.12%) and T6 heat treatment.
Industries & Applications
Automotive
Aluminum wheels, engine blocks, cylinder heads, suspension components, structural parts
Aerospace
Landing gear components, wing spars, fuselage frames
Defense
Missile components, military vehicle parts
Energy
Turbine components, impellers, industrial installations
Special Notes
The "A" prefix designates a higher purity version. A356.2 enforces ≤0.12% iron, eliminating brittle iron-rich intermetallic phases. This yields ~20% better toughness, with 6–10% elongation vs 2–4% in standard 356. For automotive wheels and safety-critical structural parts, we manufacture A356.2 from primary aluminum base to guarantee low iron and trace content.
Frequently Asked Questions
What is AlSi7Mg (A356) alloy and what is it used for?
A356/AlSi7Mg is an Al-Si-Mg casting alloy of the 3xx.x series, regarded as the most important aluminum casting alloy in the world thanks to its excellent fluidity and castability. It is used in automotive components such as aluminum wheels, engine blocks, cylinder heads and suspension parts, as well as in aerospace (landing gear, wing spars), defense and energy applications (turbine components, impellers).
What is the chemical composition of A356 and what do its alloying elements do?
Its base is aluminum with 6.50–7.50% silicon, which provides the excellent fluidity needed to fill complex molds, and 0.25–0.45% magnesium, which makes it heat-treatable by forming hardening precipitates. Iron is kept low (≤0.20% in A356 and ≤0.12% in A356.2), with copper, manganese, zinc and titanium restricted (≤0.10–0.20%). The low iron eliminates brittle intermetallic phases and improves ductility.
Is A356 heat-treatable, and what strength does it reach?
Yes, it is heat-treatable across multiple tempers (F, T5, T6, T61, T71). In the T6 temper it reaches a tensile strength (UTS) of ~310 MPa, a yield strength of ~230 MPa and a hardness of ~75 HB. Elongation ranges from 3–10%, reaching 6–10% in the A356.2 T6 version owing to its lower iron content.
Why is A356.2 preferred for wheels and safety-critical parts?
The "A" prefix designates a higher-purity version, and A356.2 enforces ≤0.12% iron, eliminating the brittle iron-rich intermetallic phases. This raises toughness by about 20% and increases elongation to 6–10% (versus 2–4% in standard 356), making it ideal for aluminum wheels and structural automotive components where ductility and fatigue life are critical.
How does A356 differ from its sibling alloy A357?
Both share the same silicon (6.5–7.5%), but A357 (AlSi7Mg0.6) has higher magnesium (0.45–0.60% versus A356's 0.25–0.45%), which increases mechanical strength: ~345 MPa UTS in A357 against ~310 MPa in A356 after T6. A357 is the premium high-strength version for safety-critical structural and aerospace parts; A356 offers a balance of strength, ductility and castability.
Does TP make A356 from primary aluminum or from recycled scrap?
We manufacture this alloy from both primary and secondary aluminum base, depending on customer specifications. For automotive wheels and safety-critical structural parts we produce A356.2 from a primary aluminum base, which guarantees the low iron (≤0.12%) and trace content required for maximum purity and ductility.
Under which international designations is A356 known?
It is identified as A356.0 / A356.2 under AA (USA), EN AC-42100 · AlSi7Mg0.3 in Europe, G-AlSi7Mg / 3.2371 under DIN (Germany), AlSi7Mg under ISO, AC4C under JIS (Japan), A-S7G03 under NF (France) and G-AlSi7Mg under UNI (Italy). It has a density of 2.67 g/cm³ and a melting range of 557–615 °C.
Need AlSi7Mg (A356)?
We manufacture this alloy in ingots, donuts, and bars to your exact specifications.