Aluminum AC8B-T6
Temper · default condition
JIS AC8B
T6 = solution heat treated and artificially aged
Default specified condition for maximum strength and hardness in highly loaded pistons and heads.
Values for the T6 condition
Other AC8B tempers and conditions
AC8B is listed in 4 conditions; see the grade overview at AC8B.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As fabricated | Cheapest condition; use where dimensional stability and peak hot strength are not required. | 130 | 180 | 1.5 | 85 HB | 28 % IACS |
Cooled from hot working and artificially aged | Pick when dimensional stability and moderate strength matter more than peak strength — the common production piston condition. | 180 | 210 | 1 | 95 HB | 27 % IACS |
Solution heat treated and overaged (stabilized) | Choose for best dimensional and property stability at sustained high temperature, trading some room-temperature strength. | 205 | 250 | 1.5 | 100 HB | 28 % IACS |
T6DefaultThis page Solution heat treated and artificially aged | Default specified condition for maximum strength and hardness in highly loaded pistons and heads. | 235 | 280 | 1 | 110 HB | 25 % IACS |
What is AC8B-T6?
AC8B-T6 is AC8B in the T6 temper — default specified condition for maximum strength and hardness in highly loaded pistons and heads. AC8B-T6 has a yield strength of 235 MPa (34.1 ksi) and a tensile strength of 280 MPa (40.6 ksi) — stronger than 61% of aluminum grades. Elongation at break is 1% and the elastic modulus is 82 GPa (11.9 Msi). AC8B-T6 has a density of 2.76 g/cm³ (0.0997 lb/in³), heavier than 70% of aluminum grades. It melts at 521°C (970 °F).
Advantages
- Stiff — 82 GPa (11.9 Msi), better than 97% of aluminum grades
- High service temperature — 230°C (446 °F), better than 95% of aluminum grades
Limitations
- Limited ductility — 1%, worse than 95% of aluminum grades
- Poor heat conductor — 96 W/m·K (55.5 BTU/hr·ft·°F), worse than 95% of aluminum grades
- Low fracture toughness — 15 MPa·√m (13.7 ksi·√in), worse than 93% of aluminum grades
- Low electrical conductivity — 25 % IACS, worse than 92% of aluminum grades
- Hard to polish — 40/100, worse than 91% of aluminum grades
AC8B-T6 properties
Typical room-temperature values for AC8B-T6; 10 are specific to this condition. Other listed values are AC8B reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
AC8B-T6 has a density of 2.76 g/cm³ (0.0997 lb/in³), heavier than 70% of aluminum grades. It melts at 521°C (970 °F).
Mechanical13
AC8B-T6 has a yield strength of 235 MPa (34.1 ksi) and a tensile strength of 280 MPa (40.6 ksi) — stronger than 61% of aluminum grades. Elongation at break is 1% and the elastic modulus is 82 GPa (11.9 Msi).
Thermal6
AC8B-T6 is rated for continuous service to 230°C (446 °F). It conducts heat at 96 W/m·K (55.5 BTU/hr·ft·°F), worse than 95% of aluminum grades. Thermal expansion is 20.7 µm/m·K (11.5 µin/in·°F).
Electrical3
AC8B-T6 conducts electricity at 25 % IACS, worse than 92% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (38/100), worse than 79% of aluminum grades.
Sustainability4
Producing a kilogram of AC8B-T6 takes about 200 MJ of energy and emits 12 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 75%.
Manufacturability7
AC8B-T6's machinability is fair (50/100, worse than 65% of aluminum grades); weldability poor (22/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AC8B-T6
Is AC8B easy to machine?
Machines cleanly but the primary Si and Cu/Ni intermetallics abrade tools — use PCD or fine-grain carbide, high speed, low feed, and flood coolant; finish ring grooves after ageing.
Can AC8B be welded?
Poor fusion weldability because of the 2–4% Cu (hot cracking, loss of ageing response); repairs only by TIG with 4145/4047-type filler followed by re-ageing.
Can AC8B be formed, bent or molded?
Gravity/permanent-mold or squeeze casting alloy with good fluidity and low shrink porosity; degas and grain refine, control Fe below 1% and use controlled solidification for piston crown soundness. Not a wrought/formable alloy.
What surface finishes work on AC8B?
Take chemical conversion coating or functional hard anodizing (crown, ring groove) rather than decorative anodizing; tin or graphite skirt coatings and phosphate/paint systems are common; polishing is limited by Si particles.
AC8B 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 |
| Ni | 0.1 – 1 | 0.5 |
| Feimpurity limit | ≤ 1 | — |
| Mnimpurity limit | ≤ 0.5 | — |
| Znimpurity limit | ≤ 0.5 | — |
| Tigrain refiner / impurity limit | ≤ 0.2 | — |
| Crimpurity limit | ≤ 0.1 | — |
| Pbimpurity limit | ≤ 0.05 | — |
| Snimpurity limit | ≤ 0.05 | — |
| Al | balance | — |
AC8B-T6 — frequently asked
What is AC8B-T6 used for?
AC8B-T6 is typically used for automotive pistons, compressor pistons, air-conditioning compressor components, motorcycle and small-engine pistons, high-temperature wear bushings and ring-groove-carrying piston crowns. In short: tuned-expansion piston variant; wear-resistant Cu-Ni casting; lowest conductivity in AC8.
What is the yield strength of AC8B-T6?
AC8B-T6 has a typical yield strength of 235 MPa (34.1 ksi) and a tensile strength of 280 MPa (40.6 ksi) — stronger than 61% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is AC8B-T6 easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 65% of aluminum grades). Machines cleanly but the primary Si and Cu/Ni intermetallics abrade tools — use PCD or fine-grain carbide, high speed, low feed, and flood coolant; finish ring grooves after ageing.
Can AC8B-T6 be welded?
Not readily — weldability is rated poor (22/100). Poor fusion weldability because of the 2–4% Cu (hot cracking, loss of ageing response); repairs only by TIG with 4145/4047-type filler followed by re-ageing.
What surface finishes work on AC8B-T6?
Take chemical conversion coating or functional hard anodizing (crown, ring groove) rather than decorative anodizing; tin or graphite skirt coatings and phosphate/paint systems are common; polishing is limited by Si particles.
Can AC8B-T6 be formed, bent or molded?
Gravity/permanent-mold or squeeze casting alloy with good fluidity and low shrink porosity; degas and grain refine, control Fe below 1% and use controlled solidification for piston crown soundness. Not a wrought/formable alloy.
What is the maximum service temperature of AC8B-T6?
AC8B-T6 is rated for continuous use to about 230°C (446 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AC8B-T6 and AC8B-F?
T6 is the default condition — default specified condition for maximum strength and hardness in highly loaded pistons and heads. F: cheapest condition; use where dimensional stability and peak hot strength are not required. Yield strength is 235 MPa in T6 versus 130 MPa in F.
Sources
- JIS H 5202 Aluminium alloy castings — JSA (2010)
- ASM Handbook Vol. 2: Properties and Selection — Nonferrous Alloys (332.0 / SAE 332) — ASM International (1990)
- ASTM B108 / Aluminum Association Designations for Cast Alloys — ASTM / Aluminum Association (2018)
- GB/T 1173 (ZL109 comparable piston alloy) — 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.