Aluminum 355 · precip hard
Aluminum 355-T71
Properties of the T71 condition, compared with the other 355 tempers.
Softest heat-treated temper: best dimensional stability, machinability and toughness for elevated-temperature or long-service castings.
What is 355-T71?
355-T71 is 355 in the T71 condition — softest heat-treated temper: best dimensional stability, machinability and toughness for elevated-temperature or long-service castings. 355-T71 has a yield strength of 190 MPa (27.6 ksi) and a tensile strength of 245 MPa (35.5 ksi) — weaker than 52% of aluminum grades. Elongation at break is 2% and the elastic modulus is 71 GPa (10.3 Msi). 355-T71 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).
Advantages
- High service temperature — 200°C (392 °F), better than 90% of aluminum grades
- High electrical conductivity — 42 % IACS, better than 81% of aluminum grades
- Conducts heat well — 165 W/m·K (95.3 BTU/hr·ft·°F), better than 79% of aluminum grades
Limitations
- Limited formability — 5/100, worse than 94% of aluminum grades
- Limited ductility — 2%, worse than 87% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
355-T71 properties
Typical room-temperature values for 355-T71 — 9 properties are specific to this condition; the rest are grade-level values shared by every 355 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
355-T71 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-T71 has a yield strength of 190 MPa (27.6 ksi) and a tensile strength of 245 MPa (35.5 ksi) — weaker than 52% of aluminum grades. Elongation at break is 2% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
355-T71 is rated for continuous service to 200°C (392 °F). It conducts heat at 165 W/m·K (95.3 BTU/hr·ft·°F), better than 79% of aluminum grades. Thermal expansion is 22.4 µm/m·K (12.4 µin/in·°F).
Electrical3
355-T71 conducts electricity at 42 % IACS, better than 81% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 62% of aluminum grades.
Sustainability4
Producing a kilogram of 355-T71 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-T71's machinability is good (60/100, better than 50% of aluminum grades); weldability good (55/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 355 tempers and conditions
355 is also supplied in 4 other conditions. The full side-by-side table is on the 355 overview.
- T61Choose when maximum yield strength/hardness and wear resistance matter more than ductility.250 MPa yield · 96 HB
- T7For parts machined to tight tolerance or running hot, where growth/residual-stress stability beats peak strength.250 MPa yield · 85 HB
- T71Softest heat-treated temper: best dimensional stability, machinability and toughness for elevated-temperature or long-service castings.190 MPa yield · 75 HB
- T6Standard commercial condition — best combination of strength and residual ductility for pressure-tight structural castings.180 MPa yield · 85 HB
- T51Cheap low-distortion temper for dimensionally critical castings that do not need full T6 strength.165 MPa yield · 70 HB
Working with 355-T71
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.
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.
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 | — |
355-T71 — frequently asked
What is 355-T71 used for?
355-T71 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-T71?
355-T71 has a typical yield strength of 190 MPa (27.6 ksi) and a tensile strength of 245 MPa (35.5 ksi) — weaker than 52% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is 355-T71 easy to machine?
Reasonably — machinability is rated good (60/100, better than 50% 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-T71 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-T71?
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-T71 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-T71?
355-T71 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 355-T71?
Yes — 355-T71 is available for CNC machining with instant online pricing. 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.