332.0 (AlSi9.5Cu3)
Hypoeutectic piston alloy with copper, optimized for Mexico’s automotive cast-piston sector.
332.0 is an Al-Si-Cu-Mg piston alloy with ~9.5% silicon (hypoeutectic composition) that combines good castability, hot strength, and dimensional stability. Copper (2.0–4.0%) and magnesium contribute precipitation-hardening strength in the T5 temper, while silicon improves wear resistance and lowers the thermal expansion coefficient. It is one of the classic permanent-mold cast-piston alloys, in strong demand in the Mexican automotive sector. We manufacture it from a primary aluminum base for precise composition control.
International Nomenclature
| Standard | Designation |
|---|---|
| AA (USA) | 332.0 |
| UNS | A03320 |
| ISO | Al-Si9.5Cu3 |
Chemical Composition
| Element | Symbol | Percentage |
|---|---|---|
| Aluminum | Al | Balance |
| Silicon | Si | 8.5–10.5% |
| Copper | Cu | 2.0–4.0% |
| Magnesium | Mg | 0.50–1.5% |
| Iron | Fe | ≤1.2% |
| Manganese | Mn | ≤0.50% |
| Nickel | Ni | ≤0.50% |
| Zinc | Zn | ≤1.0% |
| Titanium | Ti | ≤0.25% |
| Others (total) | — | ≤0.50% |
Physical Properties
| Property | Value |
|---|---|
| Density | ~2.76 g/cm³ |
| Melting Range | ~521–582 °C |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength (UTS) | ~248 MPa (T5) |
| Yield Strength | ~193 MPa (T5) |
| Hardness | ~105 HB |
Key Characteristics
- Hypoeutectic piston alloy (~9.5% Si) with good hot strength
- Copper (2.0–4.0%) for precipitation hardening in the T5 temper
- Magnesium is the key discriminator versus alloy 333.0
- Good dimensional stability and wear resistance for pistons
- Suited for high-volume permanent-mold casting
Compared to Similar Alloys
332.0 (AlSi9.5Cu3) vs 336.0 (AlSi12CuNiMg)
Both are permanent-mold Al-Si-Cu cast-piston alloys, but they differ on the main metallurgical lever: 332.0 is hypoeutectic (~9.5% Si) with high copper (2.0–4.0%) for added strength, whereas 336.0 is eutectic (~12% Si) with nickel (2.0–3.0%) and low copper, a "Y-alloy / Lo-Ex" type that prioritizes a very low thermal expansion coefficient and hot strength.
| Dimension | 332.0 (AlSi9.5Cu3) | 336.0 (AlSi12CuNiMg) |
|---|---|---|
| Key alloying / composition | ~9.5% Si hypoeutectic, high Cu 2.0–4.0%, Mg 0.50–1.5%, Ni ≤0.50% | ~12% Si eutectic, Ni 2.0–3.0%, low Cu 0.50–1.5%, Mg 0.7–1.3% |
| Temper & strength (UTS) | T5: ~248 MPa UTS, ~193 MPa yield, ~105 HB | T551: ~248 MPa · T65: ~324 MPa UTS, up to ~296 MPa yield, ~125 HB |
| Thermal expansion (CTE) & dimensional stability | Si lowers CTE; good dimensional stability for pistons | Very low CTE ~19–20 µm/m·K; excellent high-temperature dimensional stability |
| Casting process | High-volume permanent mold; good castability | Permanent mold; eutectic Si for fluidity and wear resistance |
| Hot strength | Good hot strength via Cu (T5 precipitation hardening) | Superior hot strength: Ni forms refractory intermetallics |
| Weldability | Poor: high Cu (up to 4%) promotes hot cracking; not a weld-oriented alloy | Limited: an Al-Si-Cu-Ni piston alloy; likewise not intended for welding |
| Typical application | High-volume cast pistons, powertrain, compressor/pump pistons (Mexican automotive) | High-performance pistons, heavy-duty diesel, motorsport, high-temperature compressors |
332.0 (AlSi9.5Cu3): Choose 332.0 for high-volume automotive cast pistons, where high copper and the T5 temper deliver good strength and dimensional stability at competitive cost.
336.0 (AlSi12CuNiMg): Choose 336.0 when you need the lowest thermal expansion coefficient, greater hot strength (Ni), and higher strength (T65 temper, ~324 MPa) for high-performance, heavy-duty diesel, or racing pistons.
Industries & Applications
Automotive
Internal-combustion engine pistons, powertrain components
Machinery
Compressor and pump pistons, heat-resistant parts
Industrial
Permanent-mold components requiring dimensional stability
Special Notes
332.0 has a hypoeutectic composition (~9.5% Si, below the ~12.6% Al-Si eutectic point), not near-eutectic. Magnesium (0.50–1.5%) is the key discriminator that differentiates it from alloy 333.0. It is classically heat-treated to the T5 temper (artificial aging without solution treatment) for cast pistons. We manufacture it from a primary aluminum base for precise composition and trace control.
Frequently Asked Questions
What is alloy 332.0 (AlSi9.5Cu3) and what is it used for?
332.0 is an Al-Si-Cu-Mg casting alloy with a hypoeutectic composition (~9.5% silicon) designed for pistons. It combines good castability, hot strength, and dimensional stability, making it one of the classic permanent-mold cast-piston alloys. Its primary application is the Mexican automotive sector: internal-combustion engine pistons and powertrain components, plus compressor and pump pistons.
What is the chemical composition of 332.0 and what does each element do?
On an aluminum base, 332.0 contains silicon 8.5–10.5%, copper 2.0–4.0%, magnesium 0.50–1.5%, plus limits on iron (≤1.2%), manganese (≤0.50%), nickel (≤0.50%), and zinc (≤1.0%). Silicon improves castability and wear resistance and lowers the thermal expansion coefficient; copper and magnesium provide precipitation-hardening strength in the T5 temper. Magnesium is also the key discriminator that differentiates it from alloy 333.0.
Is 332.0 heat-treatable? Which temper is used and what strength does it reach?
Yes. 332.0 is classically heat-treated to the T5 temper (artificial aging without prior solution treatment) for cast pistons. In T5 it reaches a tensile strength (UTS) of ~248 MPa, a yield strength of ~193 MPa, and a hardness of ~105 HB. The precipitation hardening is provided by the copper and magnesium in the alloy.
Which casting process is 332.0 best suited for?
332.0 is suited for high-volume permanent-mold casting, the classic process for automotive pistons. Its good castability and dimensional stability make it appropriate for permanent-mold components requiring precision. Its melting range is approximately 521–582 °C and its density is ~2.76 g/cm³.
What is the difference between 332.0 and 336.0 (formerly A332.0)?
Although their names are similar, they are distinct alloys. 332.0 is hypoeutectic (~9.5% Si, below the ~12.6% Al-Si eutectic) and is hardened with copper and magnesium. 336.0 (formerly designated A332.0) is a eutectic (~12% Si) "Y-alloy / Lo-Ex" type with nickel additions (2.0–3.0%) that form refractory intermetallics and give it a very low thermal expansion coefficient (~19–20 µm/m·K). 336.0 targets high-performance engine pistons; 332.0 targets high-volume cast pistons.
How does Transformación Puebla manufacture 332.0, and why from a primary aluminum base?
We manufacture 332.0 from a primary aluminum base to achieve precise control of the composition and trace elements. This matters in a piston alloy, where silicon (8.5–10.5%), copper (2.0–4.0%), and magnesium (0.50–1.5%) must be held within tight ranges to ensure hot strength and dimensional stability. Using a primary base keeps impurities such as iron (≤1.2%) low.
Need 332.0 (AlSi9.5Cu3)?
We manufacture this alloy in ingots, donuts, and bars to your exact specifications.