Aluminum 357
AA 357 · UNS A03570 · EN AlSi7Mg
357 (A03570) is a high-purity Al-7Si-0.5Mg casting alloy with iron held below 0.15% and a higher magnesium level than A356, which raises strength after heat treatment.
357 tempers and conditions
357 is supplied in 5 conditions, soft to hard.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
T5, stress relieved by stretching | Use for moderate strength with minimum distortion/residual stress, since no solution quench is applied. | 150 | 200 | 2.5 | 65 HB | 41 % IACS |
Solution heat treated and overaged (stabilized) | Pick for dimensional/thermal stability and best toughness at slightly reduced strength (elevated-temperature service). | 235 | 275 | 6 | 80 HB | 42 % IACS |
Solution heat treated and artificially aged | Standard high-strength condition for structural sand, permanent-mould and investment castings. | 275 | 330 | 5 | 90 HB | 39 % IACS |
T6 variant, underaged | Aerospace peak-aged condition (typically A357 with Be/Ti refinement) for maximum strength with useful ductility. | 290 | 360 | 5 | 100 HB | 39 % IACS |
T6, heat treated by the user | Choose when the highest static strength is required and elongation can be traded down; common for HIPed/densified premium castings. | 310 | 370 | 4 | 105 HB | 38 % IACS |
What is 357?
357 (A03570) is a high-purity Al-7Si-0.5Mg casting alloy with iron held below 0.15% and a higher magnesium level than A356, which raises strength after heat treatment. It offers good fluidity, pressure tightness and weld repairability, and in T6/T61 it delivers strong static and fatigue properties in sand, permanent-mould, low-pressure and investment castings. Strength depends entirely on solution treatment plus ageing, elongation is sensitive to casting defects and dendrite size, and the silicon phase makes decorative anodizing grey. A356 is the lower-cost alternative when peak properties are not required. 357 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 557°C (1,035 °F). 357 has a yield strength of 275 MPa (39.9 ksi) and a tensile strength of 330 MPa (47.9 ksi) — stronger than 70% of aluminum grades. Elongation at break is 5% and the elastic modulus is 72 GPa (10.4 Msi).
What is 357 used for?
- Aerospace structural castings
- Helicopter gearbox and transmission housings
- Investment-cast brackets and fittings
- Low-pressure cast wheels
- Pump and valve housings
- Thin-wall pressure-tight enclosures
Advantages
- Readily welded — 85/100, better than 79% of aluminum grades
Limitations
- Limited formability — 10/100, worse than 80% of aluminum grades
357 properties
Typical room-temperature values; bars are the position among aluminum grades.
Physical3
357 has a density of 2.68 g/cm³ (0.0968 lb/in³), lighter than 72% of aluminum grades. It melts at 557°C (1,035 °F).
Mechanical12
357 has a yield strength of 275 MPa (39.9 ksi) and a tensile strength of 330 MPa (47.9 ksi) — stronger than 70% of aluminum grades. Elongation at break is 5% and the elastic modulus is 72 GPa (10.4 Msi).
Thermal6
357 is rated for continuous service to 150°C (302 °F). It conducts heat at 152 W/m·K (87.8 BTU/hr·ft·°F), better than 66% of aluminum grades. Thermal expansion is 21.5 µm/m·K (11.9 µin/in·°F).
Electrical3
357 conducts electricity at 39 % IACS, better than 65% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (58/100), better than 57% of aluminum grades.
Sustainability4
Producing a kilogram of 357 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 25%.
Manufacturability7
357's machinability is good (65/100, better than 62% of aluminum grades); weldability excellent (85/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the aluminum family
Yield strength against density for every aluminum grade FabDigit runs. 357 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 357
Is 357 easy to machine?
Machines cleanly in T6 with sharp positive-rake carbide or PCD tooling and high speeds; eutectic Si is abrasive, so avoid HSS for volume work and flood-cool to prevent built-up edge.
Can 357 be welded?
Very good gas-tungsten/laser weldability and weld-repairable per AMS/AWS practice with 4043 or 4047 filler; re-solution + re-age locally welded T6 parts to restore properties.
Can 357 be formed, bent or molded?
Foundry alloy with excellent fluidity for thin-wall sand, permanent-mould, low-pressure and investment casting; Sr/Na modification plus Ti-B refinement and controlled solidification (or HIP) maximize elongation — not a cold-forming alloy.
Manufacturability
The process limits FabDigit applies to 357. Every 357 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better65 / 100 |
|---|---|
| ISO material group | N.1 |
| Cutting speed (rough / finish) | 350 / 420 m/min |
| Minimum wall | 0.5 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 8× diameter |
| Best surface (machined / polished) | Ra 0.8 / — |
| Hardenable after machining | No |
357 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Si | 6.5 – 7.5 | 7 |
| Mgraised vs A356 for higher aged strength | 0.45 – 0.6 | 0.52 |
| Felow Fe required for ductility | ≤ 0.15 | |
| Cu | ≤ 0.05 | |
| Mn | ≤ 0.03 | |
| Zn | ≤ 0.05 | |
| Tigrain refinement | ≤ 0.2 | 0.12 |
| Others (each)total 0.15 max | ≤ 0.05 | |
| Al | balance |
What surface finishes work on 357?
Takes chromate/anodic protective coatings and paint well; hard anodize is practical but decorative anodizing turns grey and blotchy from the Si phase, so most parts are painted, chem-filmed or powder coated.
Surface treatments FabDigit runs on aluminum parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Conversion Coating
PVD Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 357 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A03570
- EN / DIN / Werkstoff-Nr.
- AlSi7Mg
How much does 357 cost?
357 is a standard-cost aluminum ($$), cheaper than about 81% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
357 — frequently asked
What is 357 used for?
357 is typically used for aerospace structural castings, helicopter gearbox and transmission housings, investment-cast brackets and fittings, low-pressure cast wheels, pump and valve housings and thin-wall pressure-tight enclosures. In short: premium sand cast.
What is the yield strength of 357?
357 has a typical yield strength of 275 MPa (39.9 ksi) and a tensile strength of 330 MPa (47.9 ksi) — stronger than 70% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is 357 easy to machine?
Reasonably — machinability is rated good (65/100, better than 62% of aluminum grades). Machines cleanly in T6 with sharp positive-rake carbide or PCD tooling and high speeds; eutectic Si is abrasive, so avoid HSS for volume work and flood-cool to prevent built-up edge.
Can 357 be welded?
Yes — weldability is rated excellent (85/100). Very good gas-tungsten/laser weldability and weld-repairable per AMS/AWS practice with 4043 or 4047 filler; re-solution + re-age locally welded T6 parts to restore properties.
What surface finishes work on 357?
Takes chromate/anodic protective coatings and paint well; hard anodize is practical but decorative anodizing turns grey and blotchy from the Si phase, so most parts are painted, chem-filmed or powder coated.
Can 357 be formed, bent or molded?
Foundry alloy with excellent fluidity for thin-wall sand, permanent-mould, low-pressure and investment casting; Sr/Na modification plus Ti-B refinement and controlled solidification (or HIP) maximize elongation — not a cold-forming alloy.
What is the maximum service temperature of 357?
357 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 357 cost?
357 is a standard-cost aluminum ($$), cheaper than about 81% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in 357?
Yes — 357 is available for CNC machining; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- Aluminum Association Teal Sheets — Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot — The Aluminum Association (2015)
- ASTM B26/B26M — Aluminum-Alloy Sand Castings — ASTM International (2018)
- ASTM B108/B108M — Aluminum-Alloy Permanent Mold Castings — ASTM International (2019)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- GB/T 1173 (ZL101A comparable grade) — SAC (2013)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.