Aluminum AC8C-T6
Temper · default condition
JIS AC8C
T6 = solution heat treated and artificially aged
Default high-strength condition for highly loaded pistons, compressor parts and heat-resistant structural castings.
Values for the T6 condition
Other AC8C tempers and conditions
AC8C is listed in 4 conditions; see the grade overview at AC8C.
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 |
T6DefaultThis page 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-T6?
AC8C-T6 is AC8C in the T6 temper — default high-strength condition for highly loaded pistons, compressor parts and heat-resistant structural castings. AC8C-T6 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). AC8C-T6 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).
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-T6 properties
Typical room-temperature values for AC8C-T6; 11 are specific to this condition. Other listed values are AC8C reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
AC8C-T6 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-T6 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-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 20.5 µm/m·K (11.4 µin/in·°F).
Electrical3
AC8C-T6 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-T6 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-T6'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. Confirm any required mill or lot documentation when quoting.
Working with AC8C-T6
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.
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.
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 | — |
AC8C-T6 — frequently asked
What is AC8C-T6 used for?
AC8C-T6 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-T6?
AC8C-T6 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-T6 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-T6 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-T6?
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-T6 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-T6?
AC8C-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 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.