Aluminum AC9A
JIS AC9A
AC9A is a JIS hypereutectic Al-Si casting alloy (A390.0) in which primary silicon crystals deliver very low thermal expansion and high wear resistance.
Reference datasheet — AC9A 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
AC9A tempers and conditions
AC9A 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 | As-cast condition; lowest cost, used where dimensional stability matters more than strength. | 140 | 165 | 0.5 | 90 HB | 26 % IACS |
Solution heat treated and overaged (stabilized) | Overaged for maximum dimensional stability at elevated temperature; pick for pistons running hot for long durations. | 160 | 180 | 0.6 | 100 HB | 27 % IACS |
Cooled from hot working and artificially aged | Low-distortion aging straight from the mould; standard for mass-produced gravity/low-pressure cast pistons. | 170 | 190 | 0.4 | 105 HB | 26 % IACS |
T6Default Solution heat treated and artificially aged | Peak-strength, peak-hardness condition — choose for highly loaded pistons and wear surfaces. | 190 | 210 | 0.4 | 135 HB | 24 % IACS |
What is AC9A?
AC9A is a JIS hypereutectic Al-Si casting alloy (A390.0) in which primary silicon crystals deliver very low thermal expansion and high wear resistance. Typical properties are 210 MPa tensile, 190 MPa yield, 135 HB, 120 W/m·K, 24% IACS and a 250 °C service limit, produced by gravity, low-pressure or squeeze casting in F, T5, T6 and T7. The costs are a machinability score of 25, which effectively requires PCD tooling, and 0.4% elongation, so the material is brittle and not structurally weldable. Near-eutectic AC8A is the easier-to-process alternative. AC9A has a density of 2.66 g/cm³ (0.0961 lb/in³), lighter than 84% of aluminum grades. It melts at 510°C (950 °F). AC9A has a yield strength of 190 MPa (27.6 ksi) and a tensile strength of 210 MPa (30.5 ksi) — weaker than 52% of aluminum grades. Elongation at break is 0.4% and the elastic modulus is 88 GPa (12.8 Msi).
What is AC9A used for?
- High-performance engine pistons
- Wear-resistant sleeves
- Cylinder liners
- Compressor pistons
- Linerless cylinder blocks
- Pump wear plates
Advantages
- Stiff — 88 GPa (12.8 Msi), better than 98% of aluminum grades
- High service temperature — 250°C (482 °F), better than 97% of aluminum grades
- Low embodied carbon — 10.5 kg CO₂/kg, better than 95% of aluminum grades
Limitations
- Limited ductility — 0.4%, worse than 100% of aluminum grades
- Low fracture toughness — 11 MPa·√m (10 ksi·√in), worse than 100% of aluminum grades
- Difficult to machine — 25/100, worse than 96% of aluminum grades
- Low electrical conductivity — 24 % IACS, worse than 95% of aluminum grades
- Limited formability — 5/100, worse than 94% of aluminum grades
AC9A properties
Typical room-temperature values for AC9A-T6; bars are the position among aluminum grades.
Physical3
AC9A has a density of 2.66 g/cm³ (0.0961 lb/in³), lighter than 84% of aluminum grades. It melts at 510°C (950 °F).
Mechanical16
AC9A has a yield strength of 190 MPa (27.6 ksi) and a tensile strength of 210 MPa (30.5 ksi) — weaker than 52% of aluminum grades. Elongation at break is 0.4% and the elastic modulus is 88 GPa (12.8 Msi).
Thermal6
AC9A is rated for continuous service to 250°C (482 °F). It conducts heat at 120 W/m·K (69.3 BTU/hr·ft·°F), worse than 80% of aluminum grades. Thermal expansion is 17 µm/m·K (9.44 µin/in·°F).
Electrical3
AC9A conducts electricity at 24 % IACS, worse than 95% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (44/100), worse than 65% of aluminum grades.
Sustainability4
Producing a kilogram of AC9A takes about 155 MJ of energy and emits 10.5 kg of CO₂ — less than 94% of aluminum grades. Typical recycled content is 35%.
Manufacturability8
AC9A's machinability is poor (25/100, worse than 96% of aluminum grades); weldability poor (20/100); 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. AC9A is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AC9A
Is AC9A easy to machine?
Primary silicon crystals are highly abrasive — use PCD or diamond-coated tooling, high speed / light feed with flood coolant; carbide tools wear out rapidly.
Can AC9A be welded?
Essentially non-weldable for structural repair — Cu-bearing hypereutectic casting is hot-crack prone; use 4047/4145 filler only for cosmetic repair with preheat.
Can AC9A be formed, bent or molded?
Gravity, low-pressure or squeeze cast at 730–780 °C with phosphorus (Cu-P / P-Cu master alloy) modification to refine primary Si; avoid Na/Sr modifiers which coarsen primary Si.
AC9A 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 |
|---|---|---|
| Sihypereutectic; P-modified to refine primary Si | 22 – 24 | 23 |
| Cu | 0.5 – 1.5 | 1 |
| Mg | 0.5 – 1.5 | 1 |
| Nielevated-temperature strength | 0.5 – 1.5 | 1 |
| Fe | ≤ 0.8 | 0.5 |
| Mn | ≤ 0.5 | |
| Zn | ≤ 0.2 | |
| Ti | ≤ 0.2 | |
| Cr | ≤ 0.1 | |
| Sn | ≤ 0.05 | |
| Pb | ≤ 0.05 | |
| Al | balance |
What surface finishes work on AC9A?
Hard anodize or ferrous/graphite coating for ring-groove and skirt wear areas; decorative anodizing gives a dark, mottled film — tin/graphite skirt coating is the common alternative.
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 AC9A in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- A390.0
How much does AC9A cost?
AC9A 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.
AC9A — frequently asked
What is AC9A used for?
AC9A is typically used for high-performance engine pistons, wear-resistant sleeves, cylinder liners, compressor pistons, linerless cylinder blocks and pump wear plates. In short: hypereutectic wear grade; lowest thermal expansion; requires PCD tooling.
What is the yield strength of AC9A?
AC9A has a typical yield strength of 190 MPa (27.6 ksi) and a tensile strength of 210 MPa (30.5 ksi) — weaker than 52% of aluminum grades. Strength varies by condition: see the 4 listed tempers.
Is AC9A easy to machine?
Not especially — machinability is rated poor (25/100, worse than 96% of aluminum grades). Primary silicon crystals are highly abrasive — use PCD or diamond-coated tooling, high speed / light feed with flood coolant; carbide tools wear out rapidly.
Can AC9A be welded?
Not readily — weldability is rated poor (20/100). Essentially non-weldable for structural repair — Cu-bearing hypereutectic casting is hot-crack prone; use 4047/4145 filler only for cosmetic repair with preheat.
What surface finishes work on AC9A?
Hard anodize or ferrous/graphite coating for ring-groove and skirt wear areas; decorative anodizing gives a dark, mottled film — tin/graphite skirt coating is the common alternative.
Can AC9A be formed, bent or molded?
Gravity, low-pressure or squeeze cast at 730–780 °C with phosphorus (Cu-P / P-Cu master alloy) modification to refine primary Si; avoid Na/Sr modifiers which coarsen primary Si.
What is the maximum service temperature of AC9A?
AC9A 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 AC9A-T6 and AC9A-F?
T6 is the default condition — peak-strength, peak-hardness condition — choose for highly loaded pistons and wear surfaces. F: as-cast condition; lowest cost, used where dimensional stability matters more than strength. Yield strength is 190 MPa in T6 versus 140 MPa in F.
How much does AC9A cost?
AC9A 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)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- ASM Specialty Handbook: Aluminum and Aluminum Alloys — ASM International (1993)
- ASTM B108 / Aluminum Association Pink Sheets (A390.0) — ASTM / AA (2018)
- GB/T 1173 (ZL109 ) — 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.