Aluminum 331.0-T6
Temper · default condition
AA 331.0 · UNS A03310
T6 = solution heat treated and artificially aged
Default high-strength condition: full solution + peak age for maximum hardness and wear resistance in pistons and highly loaded permanent-mold parts.
Values for the T6 condition
Other 331.0 tempers and conditions
331.0 is listed in 3 conditions; see the grade overview at 331.0.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Untreated permanent-mold castings; lowest cost, used where strength and dimensional stability at temperature are not critical. | 110 | 165 | 1.5 | 70 HB | 30 % IACS |
Cooled from hot working and artificially aged | Pick when dimensional stability and growth resistance at engine temperature matter more than peak strength — the classic piston condition. | 150 | 205 | 1 | 85 HB | 29 % IACS |
T6DefaultThis page Solution heat treated and artificially aged | Default high-strength condition: full solution + peak age for maximum hardness and wear resistance in pistons and highly loaded permanent-mold parts. | 195 | 250 | 1 | 95 HB | 26 % IACS |
What is 331.0-T6?
331.0-T6 is 331.0 in the T6 temper — default high-strength condition: full solution + peak age for maximum hardness and wear resistance in pistons and highly loaded permanent-mold parts. 331.0-T6 has a yield strength of 195 MPa (28.3 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 51% of aluminum grades. Elongation at break is 1% and the elastic modulus is 79 GPa (11.5 Msi). 331.0-T6 has a density of 2.72 g/cm³ (0.0983 lb/in³), heavier than 57% of aluminum grades. It melts at 538°C (1,000 °F).
Advantages
- High service temperature — 200°C (392 °F), better than 90% of aluminum grades
Limitations
- Limited ductility — 1%, worse than 95% of aluminum grades
- Limited formability — 5/100, worse than 94% of aluminum grades
- Hard to polish — 40/100, worse than 91% of aluminum grades
- Low electrical conductivity — 26 % IACS, worse than 90% of aluminum grades
- Poor heat conductor — 110 W/m·K (63.6 BTU/hr·ft·°F), worse than 88% of aluminum grades
331.0-T6 properties
Typical room-temperature values for 331.0-T6; 11 are specific to this condition. Other listed values are 331.0 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
331.0-T6 has a density of 2.72 g/cm³ (0.0983 lb/in³), heavier than 57% of aluminum grades. It melts at 538°C (1,000 °F).
Mechanical10
331.0-T6 has a yield strength of 195 MPa (28.3 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 51% of aluminum grades. Elongation at break is 1% and the elastic modulus is 79 GPa (11.5 Msi).
Thermal6
331.0-T6 is rated for continuous service to 200°C (392 °F). It conducts heat at 110 W/m·K (63.6 BTU/hr·ft·°F), worse than 88% of aluminum grades. Thermal expansion is 19.3 µm/m·K (10.7 µin/in·°F).
Electrical3
331.0-T6 conducts electricity at 26 % IACS, worse than 90% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 69% of aluminum grades.
Sustainability4
Producing a kilogram of 331.0-T6 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 70%.
Manufacturability8
331.0-T6's machinability is fair (40/100, worse than 81% of aluminum grades); weldability fair (35/100); formability not recommended (5/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 331.0-T6
Is 331.0 easy to machine?
Machinable but abrasive — use PCD or polished-flute carbide tooling, high speed, light feed and copious coolant; expect short tool life on the primary silicon.
Can 331.0 be welded?
Fair at best: repair by TIG/GTAW with 4145 or 4047 filler, preheat 150–200 °C and re-age afterwards; the Cu+Mg content makes it hot-crack sensitive and weld zones lose T6 properties.
Can 331.0 be formed, bent or molded?
Permanent-mold (gravity die) casting alloy with excellent fluidity and low shrinkage; not cold formable — design for as-cast net shape with generous fillets and controlled die temperature.
What surface finishes work on 331.0?
Hard (Type III) anodize is used on ring grooves and skirts for wear; decorative anodizing turns dark grey because of the silicon, so painting, phosphating, tin or ferrous coatings are common alternatives.
331.0 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 |
|---|---|---|
| Sinear-eutectic; gives low CTE, wear resistance and fluidity | 11 – 13 | 12 |
| Cuage-hardening / elevated-temperature strength | 0.5 – 1.5 | 1 |
| MgMg2Si precipitation hardening | 0.4 – 0.7 | 0.5 |
| Nithermal stability of aluminides | 0.4 – 0.7 | 0.5 |
| Feimpurity limit | ≤ 1 | — |
| Mnimpurity limit | ≤ 0.5 | — |
| Znimpurity limit | ≤ 0.5 | — |
| Tigrain refiner residual | ≤ 0.25 | — |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Albalance; limits are approximate AA-registration values for 331.0 — verify against current Teal Sheets before certification | balance | — |
331.0-T6 — frequently asked
What is 331.0-T6 used for?
331.0-T6 is typically used for engine pistons, cylinder heads, piston crowns and skirts for small engines, gravity-die cast compressor pistons, wear-resistant engine housings and dimensionally stable elevated-temperature castings. In short: classic permanent-mold piston alloy; wear-resistant, dimensionally stable; abrasive, low machinability score.
What is the yield strength of 331.0-T6?
331.0-T6 has a typical yield strength of 195 MPa (28.3 ksi) and a tensile strength of 250 MPa (36.3 ksi) — stronger than 51% of aluminum grades. Strength varies by condition: see the 3 listed tempers.
Is 331.0-T6 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 81% of aluminum grades). Machinable but abrasive — use PCD or polished-flute carbide tooling, high speed, light feed and copious coolant; expect short tool life on the primary silicon.
Can 331.0-T6 be welded?
With care — weldability is rated fair (35/100). Fair at best: repair by TIG/GTAW with 4145 or 4047 filler, preheat 150–200 °C and re-age afterwards; the Cu+Mg content makes it hot-crack sensitive and weld zones lose T6 properties.
What surface finishes work on 331.0-T6?
Hard (Type III) anodize is used on ring grooves and skirts for wear; decorative anodizing turns dark grey because of the silicon, so painting, phosphating, tin or ferrous coatings are common alternatives.
Can 331.0-T6 be formed, bent or molded?
Permanent-mold (gravity die) casting alloy with excellent fluidity and low shrinkage; not cold formable — design for as-cast net shape with generous fillets and controlled die temperature.
What is the maximum service temperature of 331.0-T6?
331.0-T6 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.
What is the difference between 331.0-T6 and 331.0-F?
T6 is the default condition — default high-strength condition: full solution + peak age for maximum hardness and wear resistance in pistons and highly loaded permanent-mold parts. F: untreated permanent-mold castings; lowest cost, used where strength and dimensional stability at temperature are not critical. Yield strength is 195 MPa in T6 versus 110 MPa in F.
Sources
- Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot (Teal Sheets) — The Aluminum Association (2018)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
- GB/T 1173 (comparison basis for ZL108/ZL109 piston alloys) — 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.