Aluminum A356 · precip hard
Aluminum A356-T71
Properties of the T71 condition, compared with the other A356 tempers.
Pick for maximum thermal/dimensional stability and lowest residual stress, e.g. optical or machined precision castings, accepting reduced strength.
What is A356-T71?
A356-T71 is A356 in the T71 condition — pick for maximum thermal/dimensional stability and lowest residual stress, e.g. optical or machined precision castings, accepting reduced strength. A356-T71 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 190 MPa (27.6 ksi) — weaker than 68% of aluminum grades. Elongation at break is 4% and the elastic modulus is 72.4 GPa (10.5 Msi). A356-T71 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).
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 — 163 W/m·K (94.2 BTU/hr·ft·°F), better than 77% of aluminum grades
- Good corrosion resistance — 68/100, better than 75% of aluminum grades
A356-T71 properties
Typical room-temperature values for A356-T71 — 10 properties are specific to this condition; the rest are grade-level values shared by every A356 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
A356-T71 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).
Mechanical14
A356-T71 has a yield strength of 145 MPa (21 ksi) and a tensile strength of 190 MPa (27.6 ksi) — weaker than 68% of aluminum grades. Elongation at break is 4% and the elastic modulus is 72.4 GPa (10.5 Msi).
Thermal6
A356-T71 is rated for continuous service to 200°C (392 °F). It conducts heat at 163 W/m·K (94.2 BTU/hr·ft·°F), better than 77% of aluminum grades. Thermal expansion is 21.4 µm/m·K (11.9 µin/in·°F).
Electrical3
A356-T71 conducts electricity at 42 % IACS, better than 81% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 75% of aluminum grades.
Sustainability4
Producing a kilogram of A356-T71 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 50%.
Manufacturability8
A356-T71's machinability is good (64/100, better than 59% of aluminum grades); weldability very good (80/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other A356 tempers and conditions
A356 is also supplied in 5 other conditions. The full side-by-side table is on the A356 overview.
- T61Specify for permanent-mould, low-pressure or HIP-quality castings where the fine dendrite arm spacing allows T6 strength with much higher elongation.207 MPa yield · 90 HB
- T7Use where dimensional stability at elevated temperature and lower residual stress are more important than peak strength (engine and instrument castings).185 MPa yield · 75 HB
- T6The default structural condition: peak strength with usable ductility for wheels, suspension parts, pump and housing castings.165 MPa yield · 75 HB
- T71Pick for maximum thermal/dimensional stability and lowest residual stress, e.g. optical or machined precision castings, accepting reduced strength.145 MPa yield · 65 HB
- T51Low-cost, low-distortion temper for parts needing dimensional stability and moderate strength without the quench of a full T6.138 MPa yield · 60 HB
- T4Choose when maximum ductility and impact toughness matter more than yield strength, or when the part will be straightened/formed after solution treatment.110 MPa yield · 60 HB
Working with A356-T71
Is A356 easy to machine?
Machines cleanly with sharp positive-rake carbide or PCD at high speed; the Si eutectic is abrasive so HSS tools wear fast — flood coolant, avoid built-up edge, T6 gives better finish than as-cast.
Can A356 be welded?
Readily TIG/MIG welded with 4043 (or 4145) filler; re-solution + age after welding to restore properties, and expect porosity if the casting was impregnated or not degassed.
Can A356 be formed, bent or molded?
Foundry alloy with outstanding fluidity for sand, permanent-mould and low-pressure casting — Sr modification, Ti-B grain refining, degassing and controlled solidification set the final ductility; not suitable for cold forming.
What surface finishes work on A356?
Hard anodize for wear and chromate/e-coat/powder for appearance; clear decorative anodizing looks grey and mottled from the silicon, and porous surfaces should be resin-impregnated before plating or painting.
A356 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 former; Sr or Na modification usual | 6.5 – 7.5 | 7 |
| MgMg2Si precipitation strengthening | 0.25 – 0.45 | 0.35 |
| Felow-Fe requirement distinguishes A356 from 356 | ≤ 0.2 | 0.12 |
| Cu | ≤ 0.2 | 0.05 |
| Mn | ≤ 0.1 | 0.03 |
| Zn | ≤ 0.1 | 0.03 |
| Tigrain refinement (usually with B) | ≤ 0.2 | 0.12 |
| Others (each)total others 0.15 max | ≤ 0.05 | — |
| Al | balance | — |
A356-T71 — frequently asked
What is A356-T71 used for?
A356-T71 is typically used for aerospace castings, wheels and valve bodies. In short: heat-treatable Al-Si-Mg cast.
What is the yield strength of A356-T71?
A356-T71 has a typical yield strength of 145 MPa (21 ksi) and a tensile strength of 190 MPa (27.6 ksi) — weaker than 68% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is A356-T71 easy to machine?
Reasonably — machinability is rated good (64/100, better than 59% of aluminum grades). Machines cleanly with sharp positive-rake carbide or PCD at high speed; the Si eutectic is abrasive so HSS tools wear fast — flood coolant, avoid built-up edge, T6 gives better finish than as-cast.
Can A356-T71 be welded?
Yes — weldability is rated very good (80/100). Readily TIG/MIG welded with 4043 (or 4145) filler; re-solution + age after welding to restore properties, and expect porosity if the casting was impregnated or not degassed.
What surface finishes work on A356-T71?
Hard anodize for wear and chromate/e-coat/powder for appearance; clear decorative anodizing looks grey and mottled from the silicon, and porous surfaces should be resin-impregnated before plating or painting.
Can A356-T71 be formed, bent or molded?
Foundry alloy with outstanding fluidity for sand, permanent-mould and low-pressure casting — Sr modification, Ti-B grain refining, degassing and controlled solidification set the final ductility; not suitable for cold forming.
What is the maximum service temperature of A356-T71?
A356-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 A356-T71?
Yes — A356-T71 is available for CNC machining and casting & forging 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)
- Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot (Pink Sheets) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- GB/T 1173 (ZL101A) (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.