T6
The standard and almost universal temper for 4032 forgings and pistons.
Aerospace · forged pistons
4032 Aerospace Aluminium Forgings & Forged Pistons
4032-T6 forgings combine the low thermal expansion and wear resistance of a 12 % silicon alloy with the soundness and grain flow of a forging. They are the standard material for forged pistons in aircraft piston engines, compressors and hydraulic pumps. Metline supplies 4032 forgings and forged piston blanks to ASTM B247, legacy AMS 4145 or your drawing, worldwide.
- Alloy
- 4032 (Al-12Si-Cu-Mg-Ni)
- Temper
- T6 (solution treated and aged)
- Specs
- ASTM B247 · AMS 4145 (legacy)
- Main use
- Forged pistons, wear parts
Why pistons are forged from 4032
A piston sees combustion pressure, inertia loads and temperatures well above 200 °C at the crown, while sliding in a steel or cast-iron bore. It has to be light, strong when hot, resistant to wear and dimensionally steady as it heats up.
Cast pistons in Al-Si alloys handle most of those demands, but a forging adds strength, ductility and fatigue resistance because closed-die forging closes porosity and aligns grain flow with the piston's shape. 4032 brings the alloy advantages to the forging: about 12 % silicon for low expansion and wear resistance, nickel and copper for strength at temperature, and magnesium for a strong T6 temper.
The result is a piston that can run with tight skirt clearance, stays quiet when cold, seals well and resists scuffing. Aircraft piston engines, high-performance automotive engines, compressors and hydraulic pumps all use forged 4032 pistons for these reasons. Outside pistons, 4032 forgings are used for wear-resistant bushings, pump and valve parts and swashplates.
4032 chemical composition (wt %)
| Element | Minimum | Maximum | Role |
|---|---|---|---|
| Silicon (Si) | 11.0 | 13.5 | Low thermal expansion, wear resistance |
| Copper (Cu) | 0.50 | 1.3 | Strength and elevated-temperature strength |
| Magnesium (Mg) | 0.8 | 1.3 | Age hardening with Si |
| Nickel (Ni) | 0.50 | 1.3 | Strength retention at temperature |
| Iron (Fe) | — | 1.0 | Impurity |
| Chromium (Cr) | — | 0.10 | |
| Zinc (Zn) | — | 0.25 | Impurity |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder | About 82 – 87 % |
AMS 4145 describes the nominal composition as 12.2Si-1.1Mg-0.9Cu-0.9Ni. Some older listings give silicon as 6 – 12 % and omit nickel; those figures are wrong for 4032 and should not be accepted on a certificate.
Mechanical and physical properties of 4032-T6 forgings
ASTM B247 sets the specified minimums for 4032-T6 die forgings, including a tensile strength of about 360 MPa (52 ksi); yield and elongation minimums are given in the same table and depend on the forging type and test direction. Typical values sit somewhat higher.
| Property | Typical 4032-T6 |
|---|---|
| Tensile strength | about 380 MPa (55 ksi) |
| Yield strength (0.2 %) | about 315 MPa (46 ksi) |
| Elongation | about 5 – 9 % depending on direction and section |
| Brinell hardness | about 115 – 125 HB |
| Shear strength | about 260 MPa |
| Fatigue strength (5 × 10⁸ cycles) | about 110 MPa |
Physical properties (typical, T6)
- Density
- 2.68 g/cm³
- Modulus of elasticity
- about 79 GPa, higher than most wrought alloys
- Thermal expansion
- about 19.4 µm/m·°C (20 – 100 °C), roughly 15 – 20 % below 2xxx and 6xxx alloys
- Thermal conductivity
- about 140 – 155 W/m·K
- Melting range
- about 530 – 570 °C
- Hardness
- about 120 HB
At piston operating temperatures, 4032 keeps a useful fraction of its room-temperature strength, more than 6xxx alloys but less than 2618, which was developed specifically for long exposure at high temperature. That trade-off drives the choice between the two forging alloys.
Heat treatment and tempers
Forgings are solution heat-treated, quenched and artificially aged to T6. A typical cycle, consistent with AMS 2770 practice for wrought aluminium, is solution treatment at about 505 – 520 °C, water quench, then ageing at about 170 °C for around 10 hours. The exact cycle is fixed by the specification and qualified by the forge.
O / F
Forging stock may be supplied annealed (O) or as fabricated (F) for forging and later heat treatment.
T651 and T73
Listed on some older pages for 4032 forgings, but not standard 4032 forging tempers. T73 is a 7xxx-alloy over-ageing temper. If your drawing shows them, ask the design authority to confirm.
Some piston makers apply a stabilising heat treatment so pistons do not grow when they first see engine temperature. Where this matters, state it on the order.
Specifications for 4032 forgings
| Document | Scope | Status / note |
|---|---|---|
| ASTM B247 / B247M | Die, hand and rolled-ring forgings, including 4032-T6 | Current; normal commercial and many aerospace orders |
| SAE AMS 4145 | Forgings, 12.2Si-1.1Mg-0.9Cu-0.9Ni (4032-T6) | Cancelled by SAE in 1996 but still seen on legacy drawings; agree a replacement with the customer |
| AMS-QQ-A-367 / QQ-A-367 | Aluminium alloy forgings, general | Legacy federal / SAE document covering several alloys |
| AMS 2770 | Heat treatment of wrought aluminium parts | Process reference |
| AMS-STD-2154 | Ultrasonic inspection of wrought metals | Inspection on request |
| EN 586 / JIS H4140 | European and Japanese forging standards | For EN AW-4032 and A4032 forgings |
Forging forms we supply
Closed-die piston forgings
Near-net piston blanks with crown, skirt and pin bosses formed in the die, ready for machining.
Discs and pancakes
Upset discs for machining pistons, pump parts and valve plates where volumes do not justify dedicated dies.
Forged bar
Forged and heat-treated bar for bushes, sleeves and wear parts.
Rings
Forged or rolled rings for wear sleeves and bearing housings, to drawing.
Size limits depend on the forging route and die; we confirm feasibility for each drawing rather than quoting a general size table.
Inspection and documentation
- Chemistry and tensile tests: per heat-treat lot, reported on an EN 10204 3.1 certificate
- Hardness: Brinell checks on each forging or by sampling plan
- Macro-etch and grain flow: sectioned sample forgings to confirm flow lines follow the piston contour
- Ultrasonic inspection: to AMS-STD-2154 or the customer specification for critical parts
- Dimensional check: against the forging drawing, including machining allowance
- Traceability: heat and lot number marked on each forging or package
4032 vs 2618 forged pistons
| Factor | 4032-T6 | 2618-T61 |
|---|---|---|
| Silicon content | 11 – 13.5 % | 0.10 – 0.25 % |
| Thermal expansion | Lower (≈ 19.4 µm/m·°C) | Higher (≈ 22 µm/m·°C) |
| Cold clearance | Tighter; quieter cold start | Larger; more cold noise |
| Wear and scuff resistance | Better | Lower; often coated |
| Ductility and toughness | Lower | Higher; tolerates detonation better |
| Strength at sustained high temperature | Good | Better |
| Typical choice | Normally aspirated and moderate-output engines, compressors | High-boost, high-load and racing engines |
Applications
- Aircraft piston engines: forged pistons for general-aviation engines
- Compressors: pistons and crossheads for air and gas compressors
- Hydraulics: pump pistons, swashplates and valve parts
- Wear parts: bushes, sleeves and bearing cages running against steel
- Automotive and motorsport: forged pistons where low noise and tight clearance matter
4032 forgings are not used for airframe structure, fuel pipes, landing-gear hubs or similar parts that older listings mention; those use 2xxx, 6xxx or 7xxx forgings.
How to order 4032 forgings
- SpecifyAlloy and temper, drawing or forging envelope, quantity and the governing specification with its revision (ASTM B247, AMS 4145 where still accepted, or your OEM document).
- ConfirmWe confirm the specification can be met, the tolerance class, test requirements and delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions and surface condition; any extra tests named on the order are carried out or arranged.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 showing chemistry and mechanical results, traceable to the cast or lot number.
- Pack and shipExport packing in sealed, moisture-protected cases or on pallets, shipped by sea or air to your port or door.
References and standards
- ASTM B247 – Standard Specification for Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings, and Rolled Ring Forgings
- SAE AMS 4145 – Aluminum Alloy Forgings, 12.2Si-1.1Mg-0.9Cu-0.9Ni (4032-T6)
- SAE AMS 2770 – Heat Treatment of Wrought Aluminum Alloy Parts
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
4032 aerospace aluminium (aluminum) forgings: questions
Why use 4032 for forged pistons?
Its 12 % silicon gives low thermal expansion and good wear resistance, so pistons run with tight clearances, quietly and with little scuffing. Forging adds strength and fatigue resistance over casting.
Is AMS 4145 still a valid specification?
SAE lists AMS 4145 as cancelled (1996), although it still appears on legacy drawings. ASTM B247 covers 4032-T6 forgings and is the usual current reference; agree the replacement with your customer.
Are 4032 forgings available in T651 or T73?
T6 is the standard temper for 4032 forgings. T73 is a 7xxx over-ageing temper and does not apply; T651 is a stretched temper for plate and bar. Confirm any such call-out with the design authority.
4032 or 2618 for a high-output engine?
2618 is more ductile and better for very high cylinder pressures and detonation. 4032 suits engines where low noise, tight clearance and wear resistance matter more.
What inspection comes with 4032 forgings?
Chemistry, tensile and hardness results on a 3.1 certificate, with grain-flow macro-etch and ultrasonic inspection available on request.
Do you ship 4032 forgings internationally?
Yes. Metline supplies 4032 forgings and piston blanks worldwide from Mumbai, with export packing and certificates.
Need 4032 forgings or piston blanks?
Send the drawing, quantity, specification and inspection requirements. We will confirm feasibility and documentation.
