Aluminum 355
AA 355 · UNS A03550 · EN AlSi5Cu1Mg · also SC51A
355 (AA 355.0, A03550, SC51A) is a heat-treatable Al-5Si-1.25Cu-0.5Mg casting alloy for sand, permanent-mold and low-pressure casting, strengthened by aging of the Cu and Mg additions while retaining good castability and pressure tightness.
355 tempers and conditions
355 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 | Cheap low-distortion temper for dimensionally critical castings that do not need full T6 strength. | 165 | 200 | 1.8 | 70 HB | 43 % IACS |
Solution heat treated and artificially aged | Standard commercial condition — best combination of strength and residual ductility for pressure-tight structural castings. | 180 | 250 | 3 | 85 HB | 36 % IACS |
Solution heat treated and strongly overaged | Softest heat-treated temper: best dimensional stability, machinability and toughness for elevated-temperature or long-service castings. | 190 | 245 | 2 | 75 HB | 42 % IACS |
T6 variant, underaged | Choose when maximum yield strength/hardness and wear resistance matter more than ductility. | 250 | 280 | 1.2 | 96 HB | 37 % IACS |
Solution heat treated and overaged (stabilized) | For parts machined to tight tolerance or running hot, where growth/residual-stress stability beats peak strength. | 250 | 270 | 1 | 85 HB | 42 % IACS |
What is 355?
355 (AA 355.0, A03550, SC51A) is a heat-treatable Al-5Si-1.25Cu-0.5Mg casting alloy for sand, permanent-mold and low-pressure casting, strengthened by aging of the Cu and Mg additions while retaining good castability and pressure tightness. It is chosen for cylinder heads, water-cooled housings, pump bodies and aircraft hydraulic castings that must hold pressure without leaking and operate at 150–200 °C. The copper content lowers corrosion resistance and decorative anodizing quality compared with 356/A356, elongation is low at mostly 1–4 %, and heavy sections need good feeding and controlled heat treatment. 355 has a density of 2.71 g/cm³ (0.0979 lb/in³), heavier than 51% of aluminum grades. It melts at 546°C (1,015 °F). 355 has a yield strength of 180 MPa (26.1 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 54% of aluminum grades. Elongation at break is 3% and the elastic modulus is 71 GPa (10.3 Msi).
What is 355 used for?
- Pump housings
- Compressor bodies
- Cylinder heads
- Water-cooled crankcases and jackets
- Aircraft hydraulic valve bodies
- Pressure-tight manifolds and fittings
Advantages
- High service temperature — 175°C (347 °F), better than 83% of aluminum grades
Limitations
- Limited formability — 5/100, worse than 94% of aluminum grades
- Limited ductility — 3%, worse than 79% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
355 properties
Typical room-temperature values; bars are the position among aluminum grades.
Physical3
355 has a density of 2.71 g/cm³ (0.0979 lb/in³), heavier than 51% of aluminum grades. It melts at 546°C (1,015 °F).
Mechanical11
355 has a yield strength of 180 MPa (26.1 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 54% of aluminum grades. Elongation at break is 3% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
355 is rated for continuous service to 175°C (347 °F). It conducts heat at 151 W/m·K (87.2 BTU/hr·ft·°F), better than 63% of aluminum grades. Thermal expansion is 22.4 µm/m·K (12.4 µin/in·°F).
Electrical3
355 conducts electricity at 36 % IACS, better than 55% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 62% of aluminum grades.
Sustainability4
Producing a kilogram of 355 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 80%.
Manufacturability8
355's machinability is good (62/100, better than 55% of aluminum grades); weldability good (55/100); formability not recommended (5/100).
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. 355 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 355
Is 355 easy to machine?
Machines well in T6/T7 with PCD or polished carbide, high speed and low feed; eutectic Si is abrasive, so flood coolant and sharp edges keep built-up edge and tool wear down.
Can 355 be welded?
GTAW/GMAW with 4043 or 4145 filler is practical for repair, but Cu content raises hot-crack sensitivity — preheat 150–200 °C and re-solution + re-age locally welded structural castings.
Can 355 be formed, bent or molded?
Excellent fluidity and pressure tightness in sand, permanent-mold and low-pressure casting; use directional solidification with chills/risers in heavy sections, Sr or Na modification plus Ti-B refinement.
Manufacturability
The process limits FabDigit applies to 355. Every 355 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better62 / 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 |
355 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 | 4.5 – 5.5 | 5 |
| Cu | 1 – 1.5 | 1.25 |
| Mg | 0.4 – 0.6 | 0.5 |
| Fe0.6 max sand castings; 1.0 max permanent mold | ≤ 0.6 | |
| Mn | ≤ 0.5 | |
| Zn | ≤ 0.35 | |
| Cr | ≤ 0.25 | |
| Tigrain refiner | ≤ 0.25 | |
| Ni | ≤ 0.1 | |
| Others (each) | ≤ 0.05 | |
| Others (total) | ≤ 0.15 | |
| Al | balance |
What surface finishes work on 355?
Takes chromate/phosphate conversion coatings and paint or powder coat well; hard anodize is possible but comes out dark and mottled because of Si and Cu — avoid for decorative bright finishes.
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 355 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A03550
- EN / DIN / Werkstoff-Nr.
- AlSi5Cu1Mg
- Trade names
- SC51A
How much does 355 cost?
355 is a budget-cost aluminum ($), cheaper than about 82% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
355 — frequently asked
What is 355 used for?
355 is typically used for pump housings, compressor bodies, cylinder heads, water-cooled crankcases and jackets, aircraft hydraulic valve bodies and pressure-tight manifolds and fittings. In short: general sand cast.
What is the yield strength of 355?
355 has a typical yield strength of 180 MPa (26.1 ksi) and a tensile strength of 250 MPa (36.3 ksi) — weaker than 54% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is 355 easy to machine?
Reasonably — machinability is rated good (62/100, better than 55% of aluminum grades). Machines well in T6/T7 with PCD or polished carbide, high speed and low feed; eutectic Si is abrasive, so flood coolant and sharp edges keep built-up edge and tool wear down.
Can 355 be welded?
Yes — weldability is rated good (55/100). GTAW/GMAW with 4043 or 4145 filler is practical for repair, but Cu content raises hot-crack sensitivity — preheat 150–200 °C and re-solution + re-age locally welded structural castings.
What surface finishes work on 355?
Takes chromate/phosphate conversion coatings and paint or powder coat well; hard anodize is possible but comes out dark and mottled because of Si and Cu — avoid for decorative bright finishes.
Can 355 be formed, bent or molded?
Excellent fluidity and pressure tightness in sand, permanent-mold and low-pressure casting; use directional solidification with chills/risers in heavy sections, Sr or Na modification plus Ti-B refinement.
What is the maximum service temperature of 355?
355 is rated for continuous use to about 175°C (347 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 355 cost?
355 is a budget-cost aluminum ($), cheaper than about 82% 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 355?
Yes — 355 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
- ASTM B26/B26M Aluminum-Alloy Sand Castings — ASTM International (2018)
- ASTM B108/B108M Aluminum-Alloy Permanent Mold Castings — ASTM International (2019)
- Registration Record of Aluminum Association Alloy Designations (Pink Sheets, casting alloys) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- Aluminum Casting Technology / ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- GB/T 1173 (ZL105 AlSi5Cu1Mg) — 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.