Aluminum AC8A
JIS AC8A
AC8A is a JIS Al-Si-Cu-Ni-Mg permanent-mould casting alloy (A332.0, EN AC-48000, 336.0) developed for internal-combustion engine pistons, where Cu, Ni and Mg phases retain strength at temperature and the near-eutectic silicon keeps expansion low.
Reference datasheet — AC8A 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
AC8A tempers and conditions
AC8A is supplied in 4 conditions, soft to hard. T6 is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Cheapest condition; used where dimensional stability and peak hot strength are not critical. | 140 | 190 | 1.5 | 85 HB | 30 % IACS |
Solution heat treated and overaged (stabilized) | Pick when long-term dimensional stability and creep resistance at elevated engine temperature outrank peak strength. | 195 | 255 | 1.5 | 95 HB | 30 % IACS |
Cooled from hot working and artificially aged | Low-distortion, low-cost strengthening route for mass-produced pistons where full T6 strength is not needed. | 205 | 255 | 1 | 100 HB | 29 % IACS |
T6Default Solution heat treated and artificially aged | Standard condition for high-performance pistons: highest strength and hardness of the AC8A tempers. | 240 | 285 | 1 | 115 HB | 28 % IACS |
What is AC8A?
AC8A is a JIS Al-Si-Cu-Ni-Mg permanent-mould casting alloy (A332.0, EN AC-48000, 336.0) developed for internal-combustion engine pistons, where Cu, Ni and Mg phases retain strength at temperature and the near-eutectic silicon keeps expansion low. Typical values are 285 MPa tensile, 240 MPa yield, 115 HB, 130 W/m·K and a 250 °C service limit, available in F, T5, T6 and T7. Elongation of only 1%, machinability of 50 from abrasive silicon and Cu-driven hot cracking make it brittle and unsuitable for structural welding. AC9A is the alternative when lower expansion and higher wear resistance are required. AC8A has a density of 2.7 g/cm³ (0.0975 lb/in³), lighter than 59% of aluminum grades. It melts at 525°C (977 °F). AC8A has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 285 MPa (41.3 ksi) — stronger than 63% of aluminum grades. Elongation at break is 1% and the elastic modulus is 82 GPa (11.9 Msi).
What is AC8A used for?
- automotive pistons
- small engine pistons
- high-temp wear parts
Advantages
- Stiff — 82 GPa (11.9 Msi), better than 97% of aluminum grades
- High service temperature — 250°C (482 °F), better than 97% of aluminum grades
Limitations
- Limited formability — 4/100, worse than 99% of aluminum grades
- Limited ductility — 1%, worse than 95% of aluminum grades
- Low fracture toughness — 16 MPa·√m (14.6 ksi·√in), worse than 89% of aluminum grades
- Low electrical conductivity — 28 % IACS, worse than 82% of aluminum grades
- Needs corrosion protection — 36/100, worse than 81% of aluminum grades
AC8A properties
Typical room-temperature values for AC8A-T6; bars are the position among aluminum grades.
Physical3
AC8A has a density of 2.7 g/cm³ (0.0975 lb/in³), lighter than 59% of aluminum grades. It melts at 525°C (977 °F).
Mechanical15
AC8A has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 285 MPa (41.3 ksi) — stronger than 63% of aluminum grades. Elongation at break is 1% and the elastic modulus is 82 GPa (11.9 Msi).
Thermal6
AC8A is rated for continuous service to 250°C (482 °F). It conducts heat at 130 W/m·K (75.1 BTU/hr·ft·°F), worse than 65% of aluminum grades. Thermal expansion is 19.5 µm/m·K (10.8 µin/in·°F).
Electrical3
AC8A conducts electricity at 28 % IACS, worse than 82% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (36/100), worse than 81% of aluminum grades.
Sustainability4
Producing a kilogram of AC8A takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 60%.
Manufacturability8
AC8A's machinability is fair (50/100, worse than 65% of aluminum grades); weldability poor (25/100); formability not recommended (4/100).
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. AC8A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AC8A
Is AC8A easy to machine?
Abrasive primary/eutectic silicon demands PCD or diamond-coated carbide tooling, high speed with modest feed and copious coolant; finishes well but tool wear is the cost driver.
Can AC8A be welded?
Essentially not weldable for structural repair — the Cu content promotes hot cracking; local repair only by 4047/4145 filler with preheat and immediate re-ageing.
Can AC8A be formed, bent or molded?
Gravity/permanent-mould casting with controlled Sr/P modification and directional solidification; near-eutectic composition gives good fluidity and low shrinkage but requires melt degassing to avoid porosity.
AC8A 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 | 11 – 13 | 12 |
| Cu | 0.8 – 1.3 | 1 |
| Mg | 0.7 – 1.3 | 1 |
| Niforms thermally stable aluminides | 0.8 – 1.5 | 1.1 |
| Feimpurity limit | ≤ 0.8 | |
| Mn | ≤ 0.15 | |
| Zn | ≤ 0.15 | |
| Ti | ≤ 0.2 | |
| Cr | ≤ 0.1 | |
| Pb | ≤ 0.05 | |
| Sn | ≤ 0.05 | |
| Al | balance |
What surface finishes work on AC8A?
Hard anodising or ferrous ring-groove inserts for wear surfaces, graphite/MoS2 skirt coatings and phosphate/ceramic thermal-barrier crown coatings; decorative anodise looks dark and mottled.
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 AC8A in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- A332.0AC-48000336.0
How much does AC8A cost?
AC8A 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.
AC8A — frequently asked
What is AC8A used for?
AC8A is typically used for automotive pistons, small engine pistons and high-temp wear parts. In short: standard JIS piston alloy; 250 °C service temperature; low thermal expansion casting.
What is the yield strength of AC8A?
AC8A has a typical yield strength of 240 MPa (34.8 ksi) and a tensile strength of 285 MPa (41.3 ksi) — stronger than 63% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is AC8A easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 65% of aluminum grades). Abrasive primary/eutectic silicon demands PCD or diamond-coated carbide tooling, high speed with modest feed and copious coolant; finishes well but tool wear is the cost driver.
Can AC8A be welded?
Not readily — weldability is rated poor (25/100). Essentially not weldable for structural repair — the Cu content promotes hot cracking; local repair only by 4047/4145 filler with preheat and immediate re-ageing.
What surface finishes work on AC8A?
Hard anodising or ferrous ring-groove inserts for wear surfaces, graphite/MoS2 skirt coatings and phosphate/ceramic thermal-barrier crown coatings; decorative anodise looks dark and mottled.
Can AC8A be formed, bent or molded?
Gravity/permanent-mould casting with controlled Sr/P modification and directional solidification; near-eutectic composition gives good fluidity and low shrinkage but requires melt degassing to avoid porosity.
What is the maximum service temperature of AC8A?
AC8A is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AC8A-T6 and AC8A-F?
T6 is the default condition — standard condition for high-performance pistons: highest strength and hardness of the AC8A tempers. F: cheapest condition; used where dimensional stability and peak hot strength are not critical. Yield strength is 240 MPa in T6 versus 140 MPa in F.
How much does AC8A cost?
AC8A 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
- JIS H5202 Aluminium alloy castings — JSA (2010)
- EN 1706 Aluminium and aluminium alloys — Castings (EN AC-48000 AlSi12CuNiMg) — CEN (2020)
- ASTM B26/B108 & AA designation 332.0/A332.0 — ASTM / Aluminum Association (2018)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- GB/T 1173 (ZL109 comparable piston alloy) — 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.