T4
Solution heat-treated and naturally aged. Minimum 276 MPa tensile with 14 % elongation; used where the profile is bent or stretch-formed and then aged.
Aerospace · High-strength 6xxx extrusions
6066 Aerospace Aluminium Profiles (T4, T6)
6066 extrusions give the highest strength available from a standard 6xxx alloy: at least 345 MPa tensile and 310 MPa yield in T6. They are used for machined aircraft fittings, structural angles and channels in ground equipment and defence hardware, where 6061 is not strong enough and 2xxx or 7xxx alloys are more than the job needs. Metline supplies 6066 profiles in T4, T6 and stretched tempers to ASTM B221, worldwide.
- Alloy
- 6066 (Al-Si-Mg-Cu-Mn)
- Tempers
- O, T4, T4510/11, T6, T6510/11
- T6 minimum
- 345 MPa UTS / 310 MPa YS
- Standards
- ASTM B221 · QQ-A-200/10
What 6066 profiles are used for
6066 was developed as a high-strength extrusion alloy for American aircraft and military hardware. Its high silicon, copper and manganese give T6 strength well above 6061 while keeping the simpler heat treatment and lower cost of the 6xxx family.
The same chemistry makes the alloy stiffer to push through a die, so 6066 profiles tend to be solid, fairly chunky shapes rather than thin-walled hollows: angles, tees, channels, Z-sections, I-beams, rectangular bars and machining blanks shaped close to the final part. Machining these near-net extrusions saves metal and cutting time compared with milling fittings from plate.
Because 6066 does not weld reliably and has only fair corrosion resistance, profiles are designed into bolted or riveted assemblies and given a protective finish. Used that way, they deliver a useful step up in strength for brackets, frames and fittings in secondary aircraft structure, ground equipment and defence systems.
6066 chemical composition (wt %)
Registered Aluminum Association limits followed by ASTM B221. The certificate for each lot shows the measured analysis.
| Element | Minimum | Maximum | Role in the alloy |
|---|---|---|---|
| Silicon (Si) | 0.9 | 1.8 | High Si with Mg gives a large volume of Mg2Si plus excess Si |
| Iron (Fe) | — | 0.50 | Impurity |
| Copper (Cu) | 0.7 | 1.2 | Raises aged strength substantially; lowers corrosion resistance |
| Manganese (Mn) | 0.6 | 1.1 | Strength and grain control |
| Magnesium (Mg) | 0.8 | 1.4 | Strengthens with Si |
| Chromium (Cr) | — | 0.40 | Grain control |
| Zinc (Zn) | — | 0.25 | Impurity |
| Titanium (Ti) | — | 0.20 | Grain refiner |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder | About 93 – 97 % |
Some listings cite British specification 2L84 as a 6066 equivalent. 2L84 describes an Al-Cu-Si-Mg alloy with 1.0 – 2.0 % copper, outside the 6066 range, so it should not be treated as equivalent without a full comparison.
Mechanical properties of 6066 extrusions
ASTM B221 minimums apply to all thicknesses of 6066 extruded profiles, which simplifies design compared with alloys whose limits fall with section size.
| Temper | Tensile strength (min) | Yield strength 0.2 % (min) | Elongation in 50 mm (min) |
|---|---|---|---|
| O | ≤ 200 MPa (29 ksi) max | ≤ 124 MPa (18 ksi) max | 16 % |
| T4, T4510, T4511 | 276 MPa (40 ksi) | 172 MPa (25 ksi) | 14 % |
| T42 | 276 MPa (40 ksi) | 165 MPa (24 ksi) | 14 % |
| T6, T6510, T6511 | 345 MPa (50 ksi) | 310 MPa (45 ksi) | 8 % |
| T62 | 345 MPa (50 ksi) | 290 MPa (42 ksi) | 8 % |
Typical T6 values are about 395 MPa tensile, 359 MPa yield and 12 % elongation. Figures such as 415 MPa sometimes quoted are at the top of the normal range. "T651" is a plate temper; stress-relieved extrusions are T6510 or T6511.
Physical properties
- Density
- 2.72 g/cm³ (0.098 lb/in³)
- Modulus of elasticity
- about 69 GPa (10,000 ksi)
- Thermal conductivity (T6)
- about 147 W/m·K
- Electrical conductivity (T6)
- about 37 % IACS
- Coefficient of thermal expansion
- about 23.2 µm/m·°C (20 – 100 °C)
- Melting range
- about 563 – 643 °C
6066 extrusion tempers
T4510 / T4511
T4 profiles stretched for stress relief (T4511 with minor straightening allowed).
T6
Fully heat-treated for peak strength, the normal temper for machined fittings.
T6510 / T6511
T6 profiles stretched 1 – 3 % so that they stay straight and flat when machined.
O
Annealed stock for severe forming or forging, followed by full heat treatment.
T42 / T62
User heat-treated tempers with slightly lower minimum yield.
6066 profile shapes, sizes and tolerances
Typical supply
- Standard shapes
- Angles, channels, tees, Z-sections, I-beams, rectangular and square bars
- Custom shapes
- Solid or semi-hollow profiles to drawing; simple hollows by enquiry
- Section envelope
- Open profiles up to about 850 mm wide on large presses; most under 250 mm circle
- Minimum wall
- Generally thicker than 6061 for the same shape, about 1.5 – 2 mm minimum
- Length
- Standard 6 m; cut lengths on request
- Tolerances
- ANSI H35.2 via ASTM B221, or tighter by agreement
Because 6066 extrudes more slowly than 6061, die design should favour uniform walls and generous radii.
Weight per metre equals the cross-sectional area in mm² × 0.00272. A 50 × 50 × 5 mm equal angle (about 475 mm²) weighs roughly 1.29 kg per metre in 6066.
Machining, joining and protecting 6066 profiles
Machining
Very good in T6 and T6511, with short chips. Use stretched tempers for long parts to limit distortion.
Joining
Use bolts, rivets or adhesive bonding. Fusion welding risks hot cracking and severe strength loss, so it is not used for structural joints.
Corrosion protection
Anodise, apply chromate or chromate-free conversion coating and prime; seal faying surfaces in assemblies.
Forming
Form in O or T4, then age. T6 sections tolerate only large radii.
Galvanic contact
Isolate from carbon fibre composites and stainless or titanium fasteners with sealant and wet-installed fasteners.
Inspection
Hardness and conductivity checks confirm heat treatment; ultrasonic testing can be added for critical fittings.
Typical aerospace and defence uses of 6066 profiles
- Fittings machined from near-net shapes: brackets, clips, lugs and support angles in secondary structure
- Ground support equipment: load-bearing frames, jacks, stands and towing hardware
- Defence systems: launcher rails, mounts and vehicle-mounted equipment frames
- Test and tooling: heavy rigs and fixtures that need stiffness and strength
- Forging stock: extruded bar and shapes used as pre-forms for closed-die forgings
6066 extrusions compared with 6061, 6082 and 2014
| Property | 6066-T6 | 6061-T6 | 6082-T6 | 2014-T6 |
|---|---|---|---|---|
| Minimum tensile (extrusions) | 345 MPa | 260 MPa | 290 – 310 MPa | ~415 MPa (size-dependent) |
| Minimum yield | 310 MPa | 240 MPa | 250 – 260 MPa | ~365 MPa (size-dependent) |
| Weldability | Poor | Good | Good | Poor |
| Corrosion resistance | Fair | Good | Good | Poor |
| Extrudability | Fair | Good | Good | Fair |
In short: 6061 or 6082 for welded or exposed structures, 6066 for bolted parts needing more strength, and 2014 or 7075 extrusions when strength must go higher still.
How to order 6066 aerospace profiles
- SpecifyAlloy and temper, profile drawing or standard shape and size, length, quantity and the governing specification with its revision (ASTM B221, or QQ-A-200/10 on legacy drawings).
- ConfirmWe confirm the specification can be met, the tolerance class, any extra tests and the delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions, straightness and surface condition; tests named on the order are carried out or arranged with a third party.
- 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 wooden cases or on pallets, shipped by sea or air to your port or door.
References and standards
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles and Tubes
- QQ-A-200/10 – Aluminum Alloy 6066, Bar, Rod, Shapes, Tube and Wire, Extruded (cancelled federal specification)
- ANSI H35.2 – Dimensional Tolerances for Aluminum Mill Products
- 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
6066 aerospace aluminium (aluminum) profiles: FAQs
Is 6066 stronger than 6061?
Yes. In T6 extrusions ASTM B221 requires 345 MPa tensile and 310 MPa yield for 6066, against 260 MPa and 240 MPa for 6061.
Can 6066 profiles be welded?
Not for load-bearing joints. 6066 is crack-sensitive and loses much strength near welds. Design for bolted or riveted assembly.
Does 6066 need corrosion protection?
Usually, yes. Its copper content lowers corrosion resistance, so anodising or conversion coating plus primer is normal for aerospace parts.
Which specification replaced QQ-A-200/10?
ASTM B221 is the usual replacement for 6066 extrusions on new orders; check whether your customer requires any additional aerospace inspection.
Can 6066 profiles be supplied stress relieved?
Yes, as T6510 (stretched) or T6511 (stretched with minor straightening). These keep long parts straight during machining.
Need 6066 extrusions?
Send the profile drawing or shape, temper, length and quantity. We will reply with availability, certification and delivered cost.
