Aluminum AC8C
JIS AC8C
AC8C is the third AC8-family piston alloy (A332.0), leaning hypereutectic in silicon for wear resistance while Cu, Ni and Mg provide elevated-temperature strength.
Reference datasheet — AC8C 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
AC8C tempers and conditions
AC8C 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 | Lowest-cost condition for lightly loaded housings and prototype pistons where no heat treatment budget exists. | 140 | 185 | 1.2 | 85 HB | 27 % IACS |
Cooled from hot working and artificially aged | Cheap age-only treatment that raises hardness and dimensional stability without the distortion risk of solution quenching — common for volume pistons. | 175 | 215 | 1 | 95 HB | 28 % IACS |
Solution heat treated and overaged (stabilized) | Choose when long-term dimensional stability and growth resistance at 200–250 °C matter more than peak room-temperature strength. | 200 | 235 | 1.3 | 100 HB | 30 % IACS |
T6Default Solution heat treated and artificially aged | Default high-strength condition for highly loaded pistons, compressor parts and heat-resistant structural castings. | 250 | 285 | 0.8 | 110 HB | 24 % IACS |
What is AC8C?
AC8C is the third AC8-family piston alloy (A332.0), leaning hypereutectic in silicon for wear resistance while Cu, Ni and Mg provide elevated-temperature strength. It offers 285 MPa tensile, 250 MPa yield, 110 HB, 110 W/m·K, 24% IACS and a 200 °C service limit, with machinability of 60 — the best of the AC8 group — in F, T5, T6 and T7. Elongation of 0.8% rules out bending or impact-loaded service, and 2–4% Cu makes fusion welding a repair-only operation. AC8A is the choice when the 250 °C service limit is needed. AC8C has a density of 2.74 g/cm³ (0.099 lb/in³), heavier than 64% of aluminum grades. It melts at 520°C (968 °F). AC8C has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 285 MPa (41.3 ksi) — stronger than 65% of aluminum grades. Elongation at break is 0.8% and the elastic modulus is 80 GPa (11.6 Msi).
What is AC8C used for?
- Automotive pistons
- Engine components
- Motorcycle and small-engine pistons
- Compressor pistons
- Piston crowns with cast ring grooves
- Hot-running wear parts
Advantages
- Stiff — 80 GPa (11.6 Msi), better than 95% of aluminum grades
- High service temperature — 200°C (392 °F), better than 90% of aluminum grades
Limitations
- Limited ductility — 0.8%, worse than 97% of aluminum grades
- Low electrical conductivity — 24 % IACS, worse than 95% of aluminum grades
- Limited formability — 5/100, worse than 94% of aluminum grades
- Low fracture toughness — 16 MPa·√m (14.6 ksi·√in), worse than 89% of aluminum grades
- Poor heat conductor — 110 W/m·K (63.6 BTU/hr·ft·°F), worse than 88% of aluminum grades
AC8C properties
Typical room-temperature values for AC8C-T6; bars are the position among aluminum grades.
Physical3
AC8C has a density of 2.74 g/cm³ (0.099 lb/in³), heavier than 64% of aluminum grades. It melts at 520°C (968 °F).
Mechanical13
AC8C has a yield strength of 250 MPa (36.3 ksi) and a tensile strength of 285 MPa (41.3 ksi) — stronger than 65% of aluminum grades. Elongation at break is 0.8% and the elastic modulus is 80 GPa (11.6 Msi).
Thermal6
AC8C 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 20.5 µm/m·K (11.4 µin/in·°F).
Electrical3
AC8C conducts electricity at 24 % IACS, worse than 95% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (42/100), worse than 69% of aluminum grades.
Sustainability4
Producing a kilogram of AC8C takes about 200 MJ of energy and emits 12.5 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 55%.
Manufacturability8
AC8C's machinability is good (60/100, worse than 51% of aluminum grades); weldability poor (30/100); 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. AC8C is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AC8C
Is AC8C easy to machine?
Use PCD or polished carbide at high speed with flood coolant — the eutectic Si is abrasive and chips are short; finish ring grooves after final aging to hold size.
Can AC8C be welded?
Poor fusion weldability due to 2–4 % Cu (hot cracking, low ductility); repair only with 4047/4145 filler and post-weld re-age, and avoid weld repair on load-bearing piston sections.
Can AC8C be formed, bent or molded?
Gravity permanent-mold (die) casting with controlled melt degassing, Sr/P modification and 350–400 °C mold temperature; feed heavy crown sections generously to avoid shrinkage porosity.
AC8C 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 | 8.5 – 10.5 | 9.5 |
| Cu | 2 – 4 | 3 |
| Mg | 0.5 – 1.5 | 1 |
| Nilow-Ni variant of the AC8 family | ≤ 0.5 | 0.2 |
| Feimpurity limit | ≤ 1 | 0.5 |
| Mn | ≤ 0.5 | 0.15 |
| Zn | ≤ 0.5 | 0.1 |
| Tigrain refiner | ≤ 0.2 | 0.1 |
| Cr | ≤ 0.1 | |
| Pb | ≤ 0.05 | |
| Sn | ≤ 0.05 | |
| Al | balance |
What surface finishes work on AC8C?
Typical finishes are tin or graphite skirt coating, hard anodize on the crown/top ring groove, and phosphating; decorative bright anodizing is not usable because of Si/Cu darkening.
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 AC8C in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- A332.0
How much does AC8C cost?
AC8C 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.
AC8C — frequently asked
What is AC8C used for?
AC8C is typically used for automotive pistons, engine components, motorcycle and small-engine pistons, compressor pistons, piston crowns with cast ring grooves and hot-running wear parts. In short: best-machining AC8 piston alloy; 250 MPa yield strength; balanced wear and stability.
What is the yield strength of AC8C?
AC8C has a typical yield strength of 250 MPa (36.3 ksi) and a tensile strength of 285 MPa (41.3 ksi) — stronger than 65% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is AC8C easy to machine?
Reasonably — machinability is rated good (60/100, worse than 51% of aluminum grades). Use PCD or polished carbide at high speed with flood coolant — the eutectic Si is abrasive and chips are short; finish ring grooves after final aging to hold size.
Can AC8C be welded?
Not readily — weldability is rated poor (30/100). Poor fusion weldability due to 2–4 % Cu (hot cracking, low ductility); repair only with 4047/4145 filler and post-weld re-age, and avoid weld repair on load-bearing piston sections.
What surface finishes work on AC8C?
Typical finishes are tin or graphite skirt coating, hard anodize on the crown/top ring groove, and phosphating; decorative bright anodizing is not usable because of Si/Cu darkening.
Can AC8C be formed, bent or molded?
Gravity permanent-mold (die) casting with controlled melt degassing, Sr/P modification and 350–400 °C mold temperature; feed heavy crown sections generously to avoid shrinkage porosity.
What is the maximum service temperature of AC8C?
AC8C 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 AC8C-T6 and AC8C-F?
T6 is the default condition — default high-strength condition for highly loaded pistons, compressor parts and heat-resistant structural castings. F: lowest-cost condition for lightly loaded housings and prototype pistons where no heat treatment budget exists. Yield strength is 250 MPa in T6 versus 140 MPa in F.
How much does AC8C cost?
AC8C 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 — Japanese Standards Association (2010)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
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.