Aluminum 331.0
AA 331.0 · UNS A03310
331.0 (UNS A03310, historically alloy 145) is an Al-Si-Cu-Mg permanent mold piston alloy in the ANSI/AA 3xx.x family, available in F, T5 and T6.
Reference datasheet — 331.0 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the T6 condition
331.0 tempers and conditions
331.0 is supplied in 3 conditions, soft to hard. T6 is the default FabDigit quotes; the values on this page are for it.
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 |
T6Default 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?
331.0 (UNS A03310, historically alloy 145) is an Al-Si-Cu-Mg permanent mold piston alloy in the ANSI/AA 3xx.x family, available in F, T5 and T6. It is used for gravity-die cast engine parts because of wear resistance and dimensional stability at temperature: 195 MPa yield, 250 MPa tensile, 95 HB, 110 W/m·K and service to 200 °C. Elongation is only 1 % and the machinability score of 40 reflects abrasive primary silicon, so tooling cost is higher than for 356.0; 332.0 and 339.0 are the closest piston-alloy alternatives. 331.0 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). 331.0 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).
What is 331.0 used for?
- Engine pistons
- Cylinder heads
- Piston crowns and skirts for small engines
- Gravity-die cast compressor pistons
- Wear-resistant engine housings
- Dimensionally stable elevated-temperature castings
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 properties
Typical room-temperature values for 331.0-T6; bars are the position among aluminum grades.
Physical3
331.0 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 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 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 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 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'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. 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. 331.0 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 331.0
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.
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 |
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.
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).
Organic Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 331.0 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A03310
How much does 331.0 cost?
331.0 is a standard-cost aluminum ($$), cheaper than about 71% 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.
331.0 — frequently asked
What is 331.0 used for?
331.0 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?
331.0 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 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 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?
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 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?
331.0 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.
How much does 331.0 cost?
331.0 is a standard-cost aluminum ($$), cheaper than about 71% 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.
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; 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.