T6
Solution heat-treated (press quench or separate furnace) and artificially aged. The normal delivery condition.
GB automotive extrusion alloy
6A61 T6 Automotive Aluminium Extrusions
6A61 is a Chinese GB designation for a copper-bearing Al-Mg-Si extrusion alloy, broadly in the 6061 family, listed for automotive profiles in GB/T 33910. In T6 it guarantees about 260 MPa tensile and 240 MPa proof strength. Metline supplies 6A61-T6 profiles to drawing, or an agreed 6061 / 6082 alternative, for vehicle programmes worldwide.
- Alloy
- 6A61 (GB/T 3190)
- Temper
- T6
- Min. strength (T6)
- Rm 260 / Rp0.2 240 MPa
- Standards
- GB/T 33910 · GB/T 3190
What is 6A61 aluminium?
GB/T 3190 registers a number of national 6xxx variants with a letter in the second position (6A01, 6A02, 6A16, 6A61 and others). 6A61 is one of them: silicon, magnesium and a controlled 0.25 – 0.45 % copper addition give a strong age-hardening response, and chromium controls grain structure during extrusion and solution treatment. Its chemistry and strength put it close to international 6061.
Within the automotive profile standard GB/T 33910, 6A61 is used where designers want more strength than 6063 or 6005A without moving to harder-to-extrude 7xxx alloys. Typical parts are structural brackets, frame members, sub-frame components and battery-tray rails, mostly in relatively compact solid or hollow sections.
Outside China the alloy name is not widely recognised, so export drawings often list 6061-T6 or 6082-T6 as an accepted alternative. We can supply either route and certify accordingly.
6A61 chemical composition (wt %)
The copper window (0.25 – 0.45 %) and chromium limit are the features that set 6A61 apart from 6063-type alloys. Limits below are those published for 6A61 under GB/T 3190.
| Element | Limit (%) |
|---|---|
| Silicon (Si) | 0.55 – 0.75 |
| Iron (Fe) | 0.50 max |
| Copper (Cu) | 0.25 – 0.45 |
| Manganese (Mn) | 0.10 max |
| Magnesium (Mg) | 0.75 – 1.4 |
| Chromium (Cr) | 0.30 max |
| Zinc (Zn) | 0.10 max |
| Titanium (Ti) | 0.07 max |
| Others, each | 0.05 max |
| Aluminium (Al) | Remainder |
GB alloy limits can change between editions of GB/T 3190. The mill certificate for each lot shows the actual analysis, and the edition named on your drawing governs.
6A61 mechanical properties
The minimum values are those generally listed for 6A61-T6 profiles; typical values are indicative. Thick walls and large sections may have lower minimums because they cool more slowly in the quench.
| Temper | Tensile strength Rm | Proof strength Rp0.2 | Elongation A |
|---|---|---|---|
| T6 (specified minimum) | 260 MPa | 240 MPa | 8 % |
| T6 (typical production) | about 280 – 310 MPa | about 250 – 280 MPa | 10 – 12 % |
Physical properties (typical for this alloy family)
- Density
- about 2.70 g/cm³
- Modulus of elasticity
- about 69 – 70 GPa
- Thermal conductivity
- about 160 – 180 W/m·K in T6
- Coefficient of thermal expansion
- about 23 µm/m·°C
Tempers and heat treatment
T4 for forming
Profiles can be supplied naturally aged for bending, then artificially aged to T6 after forming.
Quench control
Copper-bearing 6xxx alloys are more quench-sensitive than 6063; thicker sections need water quench to reach T6 minimums.
Ageing
Typical artificial ageing is in the range of about 170 – 180 °C for several hours, set to achieve the drawing properties.
6A61 profile range
Typical supply range
- Shapes
- Custom open and hollow sections to drawing; round, square and rectangular tube; angle, U, T, Z and H sections
- Round sections
- About 10 – 250 mm diameter, wall roughly 0.5 – 50 mm depending on section
- Rectangular sections
- Typical sizes from about 20 × 10 mm up to 100 × 80 mm and larger custom hollows
- Length
- Mill lengths or cut to drawing, according to vehicle and part
- Finish
- Mill, anodised, e-coat, powder coated or sand-blasted
Tolerances and inspection
Automotive profiles are almost always made to a part drawing, and the drawing tolerances override the general tables. Where the drawing is silent, the general tolerance standard of the order applies. Critical dimensions, such as mating faces, screw bosses and crash-relevant wall thicknesses, should be marked so they can be measured on every lot.
Tolerance and inspection framework
- General dimensional tolerances
- EN 755-9 for EN orders; ASTM B221 with ANSI H35.2 tables for ASTM orders; GB/T 14846 where a GB drawing applies
- Straightness and twist
- Per the same standards, or tighter values agreed for long members and parts that go straight into robotic welding
- Wall thickness
- Measured at drawing-defined points; closed hollow sections are checked for eccentricity and die-line quality
- Mechanical testing
- Tensile test per lot to EN ISO 6892-1 or ASTM B557, with hardness (Webster or Brinell) for in-process checks
- Microstructure
- Grain size and recrystallised surface layer checked on request, which matters for crash and bending performance
- Documentation
- EN 10204 3.1 certificate; PPAP-style first-article dimensional report on request for series parts
Joining, machining and finishing
Like other copper-bearing 6xxx alloys, 6A61 machines cleanly in T6 and can be MIG, TIG, laser or friction-stir welded, with ER4043 or ER5356 filler for arc processes. The heat-affected zone loses a large share of its T6 strength, so crash and load paths are usually designed around mechanical joints, adhesive bonding or welds in low-stress areas. The copper content means painted or anodised finishes are recommended where parts see road salt.
Mill finish
Supplied as extruded and aged, for parts that are welded, bonded or painted later in the body shop or e-coat line.
Anodising
Clear or coloured anodic films for trim, roof rails and visible parts. Film class is specified in micrometres, for example AA15 or AA20 for exterior exposure.
E-coat (electrophoretic paint)
Thin, uniform paint that penetrates hollow sections; often used after anodising for a smooth, durable finish on trim.
Powder coating
Thicker polyester or epoxy layers for chassis brackets, racks and accessories that see stone chipping.
Conversion coating
Chromium-free titanium or zirconium pre-treatment before adhesive bonding or painting, improving bond durability.
Machining and fabrication
Cut-to-length, CNC machining, punching, bending and drilling on request, so profiles arrive ready for assembly.
Where 6A61 profiles are used
- Body-in-white structures: reinforcements and cross-members
- Chassis and sub-frame parts: brackets, links and mounts machined from profiles
- Battery systems: tray rails, cross-beams and module frames
- Commercial vehicles: frames, racks and loading equipment
- Two-wheelers: frames and swing-arm sections
Older literature claims 6A61 for pistons, connecting rods or brake discs. Those parts use cast, forged or specialist materials; 6A61 extrusions are structural and bracket parts.
6A61 compared with international alloys
| Property | 6A61-T6 | 6061-T6 | 6082-T6 | 6005A-T6 |
|---|---|---|---|---|
| Copper | 0.25 – 0.45 % | 0.15 – 0.40 % | 0.10 % max | 0.30 % max |
| Min. tensile (thin wall) | 260 MPa | 260 MPa (EN 755-2) | 290 MPa | 270 MPa |
| Min. proof (thin wall) | 240 MPa | 240 MPa (EN 755-2) | 250 MPa | 225 MPa |
| Extrudability | Moderate | Moderate | Moderate | Good |
6061-T6 is the nearest international substitute in both chemistry and strength.
How to order 6A61 profiles
- SpecifyAlloy and temper (6A61-T6), section drawing, lengths, finish and annual volume; tell us whether an international alternative is acceptable.
- Confirm the standardGB/T 33910 and GB/T 3190 for GB orders, or the OEM material specification; ASTM B221 or EN 755 for alternatives.
- QuoteWe confirm availability, tolerances, certification and delivery terms (EXW, FOB, CIF or DAP) for your plant or port.
- Process and inspectProfiles are cut, finished, inspected to drawing and packed for export.
- Document and shipEach lot ships with an EN 10204 3.1 mill test certificate, lot traceability and a packing list, in seaworthy export packing. Third-party inspection can be arranged on request.
References and standards
- GB/T 3190 – Wrought aluminium and aluminium alloys: chemical composition
- GB/T 33910 – Aluminium and aluminium alloy extruded profiles for automobiles
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 755-2 – Extruded rod/bar, tube and profiles: mechanical properties
- IATF 16949 – Quality management system requirements for automotive production and relevant service parts organisations
6A61 automotive aluminium (aluminum) extrusions: frequently asked questions
Is 6A61 equivalent to 6061?
It is close: both are copper-bearing Al-Mg-Si alloys with chromium, and their T6 minimums (about 260 / 240 MPa) match. Formal equivalence must be accepted by the part owner.
What standard covers 6A61 automotive profiles?
GB/T 33910 for automotive extruded profiles, with composition in GB/T 3190.
Can 6A61 be welded?
Yes, by MIG, TIG, laser or friction stir welding, with the usual strength loss in the heat-affected zone.
What temper is supplied?
T6 normally; T4 can be supplied for parts that are bent before final ageing.
Can you supply 6061 instead?
Yes. Where the drawing allows, we supply 6061-T6 or 6082-T6 profiles to ASTM B221 or EN 755.
Need 6A61 profiles?
Send the section drawing, temper and volume. We will reply with feasibility, certification and delivered pricing.
