Aluminum 356 · precip hard
Aluminum 356-T71
Properties of the T71 condition, compared with the other 356 tempers.
Softest heat-treated condition; chosen when residual-stress relief and long-term dimensional/thermal stability outweigh strength.
What is 356-T71?
356-T71 is 356 in the T71 condition — softest heat-treated condition; chosen when residual-stress relief and long-term dimensional/thermal stability outweigh strength. 356-T71 has a yield strength of 186 MPa (27 ksi) and a tensile strength of 196 MPa (28.4 ksi) — weaker than 53% of aluminum grades. Elongation at break is 3% and the elastic modulus is 72.4 GPa (10.5 Msi). 356-T71 has a density of 2.67 g/cm³ (0.0965 lb/in³), lighter than 78% of aluminum grades. It melts at 557°C (1,035 °F).
Advantages
- High service temperature — 220°C (428 °F), better than 95% of aluminum grades
- High electrical conductivity — 41 % IACS, better than 78% of aluminum grades
Limitations
- Limited formability — 10/100, worse than 81% of aluminum grades
- Limited ductility — 3%, worse than 79% of aluminum grades
- Hard to polish — 45/100, worse than 76% of aluminum grades
356-T71 properties
Typical room-temperature values for 356-T71 — 10 properties are specific to this condition; the rest are grade-level values shared by every 356 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
356-T71 has a density of 2.67 g/cm³ (0.0965 lb/in³), lighter than 78% of aluminum grades. It melts at 557°C (1,035 °F).
Mechanical13
356-T71 has a yield strength of 186 MPa (27 ksi) and a tensile strength of 196 MPa (28.4 ksi) — weaker than 53% of aluminum grades. Elongation at break is 3% and the elastic modulus is 72.4 GPa (10.5 Msi).
Thermal6
356-T71 is rated for continuous service to 220°C (428 °F). It conducts heat at 159 W/m·K (91.9 BTU/hr·ft·°F), better than 74% of aluminum grades. Thermal expansion is 21.5 µm/m·K (11.9 µin/in·°F).
Electrical3
356-T71 conducts electricity at 41 % IACS, better than 78% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), better than 67% of aluminum grades.
Sustainability4
Producing a kilogram of 356-T71 takes about 200 MJ of energy and emits 12.5 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 60%.
Manufacturability8
356-T71's machinability is good (64/100, better than 59% of aluminum grades); weldability very good (78/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 356 tempers and conditions
356 is also supplied in 4 other conditions. The full side-by-side table is on the 356 overview.
- T61Higher-strength ageing schedule used on A356 premium-quality permanent-mould and low-pressure castings.207 MPa yield · 90 HB
- T7Over-aged for dimensional stability and higher yield at slight ductility cost; suits parts machined to tight tolerance or run warm.207 MPa yield · 75 HB
- T6Standard structural condition: best combination of strength and ductility for wheels, housings and aerospace castings.186 MPa yield · 80 HB
- T71Softest heat-treated condition; chosen when residual-stress relief and long-term dimensional/thermal stability outweigh strength.186 MPa yield · 60 HB
- T51Low-cost stabilising age (~225 °C) that raises yield and improves machinability/dimensional stability without solution-treat distortion.138 MPa yield · 60 HB
Working with 356-T71
Is 356 easy to machine?
Machines freely with sharp PCD or polished-flute carbide tooling and flood coolant; eutectic silicon is abrasive, so PCD is preferred for volume, and T6/T7 cuts cleaner than as-cast F.
Can 356 be welded?
Readily TIG/MIG welded with 4043 or 4145 filler; re-solution and re-age locally welded structural castings, and avoid welding into gas-porous or heavily impregnated regions.
Can 356 be formed, bent or molded?
Excellent fluidity and pressure tightness in sand, permanent-mould and low-pressure casting; Sr/Na modification plus Ti-B grain refining and directional solidification are key to ductility, and thin risers/hot spots cause shrinkage porosity.
What surface finishes work on 356?
Takes chemical conversion coating, primer and paint well; hard or sulfuric anodize gives a protective but dark grey, blotchy film, and mirror polishing is limited by silicon particles.
356 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 |
|---|---|---|
| Sieutectic-forming addition; Sr or Na modified in most foundry practice | 6.5 – 7.5 | 7 |
| MgA356 restricted to 0.25–0.45 % | 0.2 – 0.45 | 0.35 |
| FeA356 max 0.20 %, A356.2 ingot max 0.12 % — low Fe improves ductility | ≤ 0.6 | 0.25 |
| CuA356 max 0.20 % | ≤ 0.25 | 0.05 |
| MnA356 max 0.10 % | ≤ 0.35 | 0.05 |
| ZnA356 max 0.10 % | ≤ 0.35 | 0.05 |
| Tigrain refiner (Al-Ti-B) | ≤ 0.25 | 0.12 |
| Others (each)total 0.15 % max | ≤ 0.05 | — |
| Al | balance | — |
356-T71 — frequently asked
What is 356-T71 used for?
356-T71 is typically used for cast automotive wheels, cylinder heads and cylinder blocks, pump housings, valve bodies, structural aerospace castings and low-pressure cast intake manifolds. In short: most common sand cast.
What is the yield strength of 356-T71?
356-T71 has a typical yield strength of 186 MPa (27 ksi) and a tensile strength of 196 MPa (28.4 ksi) — weaker than 53% of aluminum grades. Strength varies by condition: see the 5 listed tempers.
Is 356-T71 easy to machine?
Reasonably — machinability is rated good (64/100, better than 59% of aluminum grades). Machines freely with sharp PCD or polished-flute carbide tooling and flood coolant; eutectic silicon is abrasive, so PCD is preferred for volume, and T6/T7 cuts cleaner than as-cast F.
Can 356-T71 be welded?
Yes — weldability is rated very good (78/100). Readily TIG/MIG welded with 4043 or 4145 filler; re-solution and re-age locally welded structural castings, and avoid welding into gas-porous or heavily impregnated regions.
What surface finishes work on 356-T71?
Takes chemical conversion coating, primer and paint well; hard or sulfuric anodize gives a protective but dark grey, blotchy film, and mirror polishing is limited by silicon particles.
Can 356-T71 be formed, bent or molded?
Excellent fluidity and pressure tightness in sand, permanent-mould and low-pressure casting; Sr/Na modification plus Ti-B grain refining and directional solidification are key to ductility, and thin risers/hot spots cause shrinkage porosity.
What is the maximum service temperature of 356-T71?
356-T71 is rated for continuous use to about 220°C (428 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 356-T71?
Yes — 356-T71 is available for CNC machining with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- Aluminum Association Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot (Pink Sheets) — The Aluminum Association (2018)
- ASTM B26/B26M — Aluminum-Alloy Sand Castings — ASTM International (2018)
- ASTM B108/B108M — Aluminum-Alloy Permanent Mold Castings — ASTM International (2019)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- GB/T 1173 (ZL101/ZL101A) — SAC (2013)
- EN 1706 AC-42000 / AC-42100 AlSi7Mg — CEN (2020)
- Aluminum Casting Technology / AFS foundry data — American Foundry Society (1997)
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.