Welding
Good fusion weldability; argon-shielded TIG and MIG are standard. Use a matching or higher-magnesium Al-Mg filler such as 5A03, 5A05 or ER5356 type.
Aerospace · Chinese-standard Al-Mg extrusions
5A03 Aircraft Extruded Aluminium Profiles & Tube
5A03 is a Chinese-standard aluminium-magnesium alloy, formerly designated LF3, with about 3.5 % magnesium. It is comparable to the Russian AMg3 and sits between 5754 and 5086 in strength. Metline supplies 5A03 extruded tube, angles, channels, flats and custom profiles in H112 and O tempers to GB/T standards for aircraft fluid lines, welded frames and fittings, worldwide.
- Alloy
- 5A03 (Al-3.5Mg-0.45Mn-0.65Si)
- Tempers
- H112, O
- Forms
- Tube, angle, channel, T, flat, custom
- Standards
- GB/T 3190 · GB/T 6892 · GB/T 4437.1
What 5A03 is and where it is used
Chinese "5Axx" designations cover aluminium-magnesium alloys registered nationally rather than with the Aluminum Association. 5A03 is the 3.5 % magnesium member of the series and has been used in Chinese and former Soviet-pattern aircraft for decades, under the older name LF3 (and AMg3 in Russian practice).
Its silicon content (0.5 – 0.8 %) is deliberately higher than in western Al-Mg alloys. The silicon improves the alloy's weldability and reduces hot cracking in fusion welds, which suits welded fuel and oil systems, tanks and frame structures.
In aircraft, 5A03 extrusions and tube are used for fuel, oil and hydraulic return lines, pneumatic lines, welded tank fittings, frames for equipment racks and cabin structures, and secondary members that must resist corrosion. It is not a primary-structure alloy; flight-critical extrusions use 2xxx and 7xxx alloys.
5A03 chemical composition (wt %)
| Element | Minimum | Maximum | Role in the alloy |
|---|---|---|---|
| Silicon (Si) | 0.50 | 0.8 | Deliberate addition; improves weldability |
| Iron (Fe) | — | 0.50 | Impurity |
| Copper (Cu) | — | 0.10 | Kept low for corrosion resistance |
| Manganese (Mn) | 0.30 | 0.6 | Adds strength, refines grain |
| Magnesium (Mg) | 3.2 | 3.8 | Main strengthening element |
| Zinc (Zn) | — | 0.20 | Impurity |
| Titanium (Ti) | — | 0.15 | Grain refiner |
| Others, each / total | — | 0.05 / 0.10 | |
| Aluminium (Al) | Remainder | — |
Limits per GB/T 3190. Some data sheets give 5A03 4.5 – 5.5 % magnesium and up to 0.6 % copper; those figures do not match the standard. The certificate supplied with each lot reports the actual analysis.
Mechanical and physical properties
| Condition | Tensile strength | Yield strength | Elongation | Notes |
|---|---|---|---|---|
| O, typical | About 230 – 245 MPa | About 100 – 120 MPa | About 20 % | Annealed tube and profiles |
| H112, typical | About 230 – 250 MPa | About 110 – 145 MPa | About 15 – 18 % | As extruded; varies with section |
| Specified minimums | Per GB/T 6892 or GB/T 4437.1 | — | — | Confirm the value for your wall thickness |
Physical properties
- Density
- About 2.67 g/cm³
- Modulus of elasticity
- About 69 – 71 GPa
- Thermal conductivity
- About 130 – 140 W/m·K
- Coefficient of thermal expansion
- About 23.5 µm/m·°C (20 – 100 °C)
- Melting range
- About 590 – 640 °C
Profiles, tube and sizes
| Form | Indicative size range |
|---|---|
| Round tube | OD about 6 – 360 mm, wall about 0.5 – 30 mm (drawn tube for small diameters) |
| Square and rectangular tube | Side about 6 – 220 mm, wall about 0.5 – 20 mm; aspect ratio up to about 6:1 |
| Angles, channels, T and Z sections | Legs or webs about 10 – 200 mm, wall about 0.5 – 20 mm |
| Flat bar | Thickness about 0.5 – 10 mm, width about 10 – 300 mm |
| Hexagon and polygon sections | About 6 – 150 mm across flats |
| Custom profiles | To customer drawing, subject to die design review |
Thin walls below about 1 mm are produced by drawing rather than extrusion. Feasibility of any custom section depends on circumscribing circle, wall ratio and tongue ratios; send the drawing for review.
Standards for extruded products
- Composition
- GB/T 3190
- Profiles
- GB/T 6892 (general industrial extrusions); dimensional tolerances per GB/T 14846
- Tube
- GB/T 4437.1 (extruded tube), GB/T 6893 (drawn tube)
- Bar
- GB/T 3191 (extruded bar)
International equivalents and substitutes
| System | Nearest grade | How close |
|---|---|---|
| China (current) | 5A03 | — |
| China (former) | LF3 | Same alloy |
| Russia / GOST | AMg3 (1530) | Very close composition |
| EN / AA | EN AW-5754 (AlMg3) | Similar Mg; lower Si, used where 5A03 is not available |
| EN / AA | EN AW-5454 (AlMg3Mn) | Similar strength; also good for warm service |
No western alloy is an exact match because of 5A03's silicon level. Substitution in an aircraft part needs approval from the design authority.
Welding, forming and corrosion
Forming
O-temper tube bends, flares and flattens well; H112 sections bend with larger radii.
Corrosion
Good resistance to atmospheric and marine corrosion. Magnesium below 4 % keeps sensitisation risk low in normal service.
Machining
Fair; soft tempers can be gummy. Use sharp tools with high rake and coolant.
Typical aircraft uses
- Fluid lines: fuel, oil, coolant and pneumatic lines that must be bent and flared
- Welded fittings: tank bosses, brackets and connectors joined to Al-Mg sheet
- Frames: equipment racks, cabin and cargo-bay secondary frames
- Ground support equipment: extruded members for stands, platforms and carts
How to order 5A03 extrusions
- SpecifyAlloy and temper, section drawing or size, length, quantity and the governing specification with its revision (GB/T 6892, GB/T 4437.1 or GB/T 3191).
- 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 and surface condition; tests named on the order are carried out or arranged with an independent laboratory.
- 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, crates or pallets, shipped by sea or air to your port or door.
References and standards
- GB/T 3190 – Chemical composition of wrought aluminium and aluminium alloys
- GB/T 6892 – Wrought aluminium and aluminium alloy extruded profiles for general engineering
- GB/T 4437.1 – Aluminium and aluminium alloy hot-extruded tubes: seamless round tubes
- GOST 4784 – Aluminium and wrought aluminium alloys: grades (AMg3)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
5A03 aircraft aluminium (aluminum) profiles: FAQs
What is the western equivalent of 5A03?
There is no exact equivalent. The Russian AMg3 is the closest match. Among EN and AA alloys, 5754 and 5454 are the nearest in magnesium content and strength, but their silicon levels differ.
Is 5A03 the same as LF3?
Yes. LF3 is the former Chinese designation; 5A03 is the current designation under GB/T 3190.
Can 5A03 be heat treated?
No. It is a non-heat-treatable alloy. Extrusions are supplied as extruded (H112) or annealed (O).
Why does 5A03 contain more silicon than 5754?
The silicon addition improves fusion weldability and resistance to hot cracking, which suits welded fuel and oil systems.
Can you extrude a custom 5A03 profile?
Yes, subject to a review of the drawing. Send the section with tolerances, length and annual quantity.
Need 5A03 tube or profiles?
Send the section, temper, length, quantity and standard. We will reply with feasibility, certification and a delivered price.
