Hot forgeability
Very plastic between roughly 420 and 500 °C, so it suits open-die and closed-die forgings with thin ribs and deep cavities.
Forging-grade 6xxx bar
6A02 (6151) Aluminium Bar
6A02 is the Chinese GB designation of a medium-strength Al-Mg-Si forging alloy that is very ductile when hot; 6151 is the closely related Aluminum Association alloy used for forgings in North America. Both are bought as extruded bar for hot forging or machining into complex, medium-stressed parts. Metline supplies 6A02 bar to GB/T 3191 and 6151 to ASTM and AMS requirements, worldwide.
- Alloy
- 6A02 (GB) ≈ 6151 (AA)
- Tempers
- O, T4, T6
- Diameter
- Approx. 8 – 150 mm extruded
- Standards
- GB/T 3191 · ASTM B247
What is 6A02 / 6151 aluminium?
6A02 belongs to the forging family of 6xxx alloys. In older Chinese practice it was called LD2, and it descends from the Soviet alloy AV (АВ). It has moderate strength, but it is soft and very plastic in the forging temperature range, so it fills complex dies with low forging loads and few laps or cracks.
6151 is the Aluminum Association alloy that occupies the same niche in the West. It also uses chromium for grain control and was historically developed for intricate forgings such as crankcases and housings. The two are close enough that buyers often treat them as alternatives, but they are not identical: 6A02 allows more copper and less iron, and both silicon and magnesium ranges differ slightly. Where a drawing calls for one, confirm the other is acceptable before substituting.
Typical forged and machined parts include engine crankcases and housings, helicopter rotor fittings, aircraft fittings of medium stress, and general machinery parts with complex shapes. Like most 6xxx alloys, its density is about 2.70 g/cm³, roughly a third of steel.
6A02 and 6151 chemical composition (wt %)
| Element | 6A02 (GB/T 3190) | 6151 (Aluminum Association) |
|---|---|---|
| Silicon (Si) | 0.50 – 1.20 | 0.6 – 1.2 |
| Iron (Fe) | ≤ 0.50 | ≤ 1.0 |
| Copper (Cu) | 0.20 – 0.60 | ≤ 0.35 |
| Manganese (Mn) | 0.15 – 0.35 (or Cr) | ≤ 0.20 |
| Magnesium (Mg) | 0.45 – 0.90 | 0.45 – 0.8 |
| Chromium (Cr) | Mn or Cr 0.15 – 0.35 | 0.15 – 0.35 |
| Zinc (Zn) | ≤ 0.20 | ≤ 0.25 |
| Titanium (Ti) | ≤ 0.15 | ≤ 0.15 |
| Others, each / total | ≤ 0.05 / 0.10 | ≤ 0.05 / 0.15 |
| Aluminium (Al) | Remainder | Remainder |
Values summarised from GB/T 3190 and the Aluminum Association registration. Each lot is certified with its actual analysis; state any tighter copper limit on the order.
Mechanical and physical properties
Strength depends strongly on temper and on whether the values are for bar or for the finished forging. Use the specified minimum of your standard for design.
| Material / temper | Tensile strength | Yield strength | Elongation | Basis |
|---|---|---|---|---|
| 6A02-T6 extruded bar | ≥ 295 MPa | — | ≥ 12 % | GB/T 3191 minimum |
| 6151-T6 forging | About 330 – 340 MPa | About 280 – 295 MPa | About 15 % | Typical |
| 6151-T6 forging | About 290 – 305 MPa | About 255 MPa | — | Indicative specified minimum (varies by standard and section) |
| 6A02-T4 | Lower; good ductility | — | High | Naturally aged |
| O (annealed) | Lowest; maximum ductility | — | High | For cold work |
Typical physical properties
- Density
- About 2.70 g/cm³
- Thermal conductivity
- About 170 – 175 W/m·K (T6)
- Coefficient of thermal expansion
- About 23 – 24 µm/m·°C
- Approximate melting range
- About 590 – 650 °C
- Hardness (T6)
- About 90 – 100 HB
How 6A02 behaves in production
Heat treatment
Solution treat around 515 – 530 °C, quench, then age naturally (T4) or artificially (T6). T6 gives the highest strength.
Machinability
Fair in the annealed state, good after quenching and ageing. Machine finished parts in T6 where possible.
Corrosion
After natural ageing it resists corrosion about as well as 3xxx and low-Mg 5xxx alloys. Artificially aged material with higher copper is more prone to intergranular attack, so low-copper material or protective finishing is advised for wet service.
Welding
Spot, seam and TIG welding are practical; as with other 6xxx alloys the weld zone loses temper.
Surface finishing
Anodises and takes conversion coatings well, which helps where artificially aged parts face moisture.
Standards and designations
| System | Designation | Scope |
|---|---|---|
| China (GB) | 6A02 (formerly LD2) | GB/T 3190 composition; GB/T 3191 extruded bar |
| Russia (GOST) | AV (АВ), 1340 | Historical parent alloy; similar but not identical |
| Aluminum Association | 6151 | Registered composition |
| UNS | A96151 | — |
| ASTM | 6151 | ASTM B247 die and hand forgings |
| SAE AMS | 6151-T6 forgings | Aerospace forging specifications on request |
6A02 bar sizes and weights
Supply range
- Extruded round bar
- Approx. 8 – 150 mm diameter
- Square and hexagonal bar
- To order
- Length
- Typically 3 m, or cut to length or forging-slug size
- Coarse-grain ring
- Reverse-extruded bar can be supplied with a limited coarse-grain ring (often ≤ 0.5 mm) on request
- Specifications
- GB/T 3191, ASTM B247 (for forgings), customer specifications
A 6A02 round bar weighs about 0.00212 × d² kg per metre (d in mm).
| Diameter (mm) | kg per metre | kg per 3 m bar |
|---|---|---|
| 23 | 1.122 | 3.37 |
| 35 | 2.598 | 7.79 |
| 40 | 3.393 | 10.18 |
| 50 | 5.301 | 15.90 |
| 60 | 7.634 | 22.90 |
| 70 | 10.39 | 31.17 |
| 80 | 13.57 | 40.72 |
| 90 | 17.18 | 51.53 |
| 100 | 21.21 | 63.62 |
| 110 | 25.66 | 76.98 |
| 120 | 30.54 | 91.61 |
| 130 | 35.84 | 107.51 |
| 150 | 47.71 | 143.14 |
Where 6A02 and 6151 bar is used
- Aerospace: medium-stressed forged fittings, air-cooled engine crankcases and rotor-hub components
- Forging shops: complex closed-die parts where flow into thin ribs is critical
- Automotive: forged and machined brackets, housings and fittings
- Marine hardware: naturally aged or protected parts for deck fittings
- Machinery: housings, couplings and shafts needing medium strength and good machined finish
6A02 compared with 6061 and 2A50
| Property | 6A02 / 6151-T6 | 6061-T6 | 2A50 / 2014-T6 |
|---|---|---|---|
| Typical tensile strength | ≈ 300 – 340 MPa | 310 MPa | ≈ 380 – 480 MPa |
| Hot forgeability | Excellent | Very good | Good |
| Corrosion resistance | Good (T4), fair (T6) | Very good | Fair |
| Weldability | Good | Good | Poor |
Choose 6A02 or 6151 when forgeability of a complex shape drives the decision. If the forging is simple and global availability matters more, 6061 is the default. For higher strength, the copper-bearing forging alloys 2A50 and 2014 are the next step, at the cost of corrosion resistance.
How to order 6A02 or 6151 bar
- SpecifyAlloy and temper, diameter, length or slug size, coarse-grain ring limit, quantity, and the governing standard (GB/T 3191, ASTM B247 or an AMS forging specification). Attach a drawing if the material will be cut or machined to shape.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessMaterial is cut to length or size on request, marked for traceability and inspected for dimensions and surface.
- DocumentEach lot ships with a mill test certificate to EN 10204 3.1 showing chemistry and mechanical results; third-party inspection can be arranged.
- ShipExport packing in seaworthy wooden cases or on pallets with moisture protection, by sea or air to your port or door.
References and standards
- GB/T 3190 – Wrought aluminium and aluminium alloys: chemical composition
- GB/T 3191 – Aluminium and aluminium alloy extruded bars
- ASTM B247 – Aluminum and Aluminum-Alloy Die Forgings, Hand Forgings, and Rolled Ring Forgings
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ASM International – Alloy Digest Al-67: Aluminum 6151 Forging Alloy
6A02 / 6151 aluminium (aluminum) bar: frequently asked questions
Is 6A02 the same as 6151?
They are close equivalents but not identical. 6A02 allows 0.20 – 0.60 % copper and limits iron to 0.50 %; 6151 limits copper to 0.35 % and allows up to 1.0 % iron. Confirm with the drawing authority before substituting.
What is 6A02 mainly used for?
Hot forgings of complex shape with medium strength: engine housings, aircraft and helicopter fittings, and machinery parts. Bar is the usual forging stock.
What is the minimum strength of 6A02-T6 bar?
GB/T 3191 sets a minimum tensile strength of about 295 MPa with at least 12 % elongation for T6 extruded bar in the common size range. Your certificate shows the actual results.
Is 6A02 corrosion resistant?
Naturally aged (T4) material has good corrosion resistance. Artificially aged (T6) material with higher copper can suffer intergranular corrosion, so anodise or paint parts for wet service or specify low copper.
What was the old name of 6A02?
In earlier Chinese standards it was LD2. Its Soviet-era parent is the alloy AV (АВ).
Do you ship 6A02 bar overseas?
Yes. Metline supplies 6A02 and 6151 bar worldwide with EN 10204 3.1 certificates and export packing.
Sourcing forging stock in 6A02 or 6151?
Send the diameter, length, temper, standard and quantity. We will confirm supply and a delivered price.
