Machining
Both alloys machine very well in T3511 and T6511 with carbide tooling. Stretched tempers keep distortion low, but balance stock removal from both sides of long beams.
Defence · Airborne launchers
2A12 and 7A09 Shaped Aluminium Tubes for Airborne Missile Launchers
Aircraft-mounted missile launchers use extruded, special-shaped high-strength aluminium tubes as their spine: the beam that carries the missile rail, the electrical harness and the launch loads while adding as little weight to the aircraft as possible. The two standard alloys are 2A12, a 2024-type Al-Cu-Mg alloy, and 7A09, a 7075-type Al-Zn-Mg-Cu alloy, supplied in stretched T3511 and T6511 tempers. This page covers their chemistry, properties, shape tolerances and surface requirements, and what to specify when ordering.
- Alloys
- 2A12 (≈ 2024) · 7A09 (≈ 7075)
- Tempers
- T3511 · T6511
- Product
- Extruded shaped (profiled) tube
- Standard
- GJB 5077 or customer drawing
What a launcher tube has to do
An airborne launcher hangs under a wing or fuselage station and must hold the missile securely through take-off, manoeuvres up to several g, landing impacts and vibration, then release it cleanly. The main beam is usually a hollow extrusion with an irregular cross-section: integral rail lands, a closed box for bending and torsional stiffness, and internal channels for cables.
Extruding that shape as one tube avoids welding or riveting a built-up beam, gives continuous grain flow along the length, and leaves only local machining for fittings. The tube must be light, very stiff, straight and free of twist, because any distortion is transferred to the rail on which the missile slides.
In China these tubes are made to GJB 5077-2001, the national military specification for aluminium alloy special-shaped tubes for airborne missile launchers. Elsewhere the same class of product is ordered as 2024 or 7075 extruded tube to ASTM B221, AMS or EN 755 standards plus the customer drawing. Metline supplies to whichever specification the programme names.
2A12 and 7A09 compared
| Aspect | 2A12 (Al-Cu-Mg) | 7A09 (Al-Zn-Mg-Cu) |
|---|---|---|
| Nearest international grade | 2024 (EN AW-2024) | 7075 (EN AW-7075), with slightly different Cu and Cr limits |
| Usual temper for tubes | T3511: solution treated, stretched, naturally aged | T6511: solution treated, stretched, artificially aged |
| Strength | High; good damage tolerance and fatigue crack growth resistance | Ultra-high; the stronger choice for compact, heavily loaded beams |
| Toughness and fatigue | Excellent fatigue performance | Good; stress-corrosion resistance better than older 7A04 |
| Corrosion | Needs anodising or paint; susceptible to intergranular attack if unprotected | Needs surface protection; over-aged tempers improve stress-corrosion resistance |
| Joining | Riveting and mechanical fastening; fusion welding not recommended | Riveting and mechanical fastening; fusion welding not recommended |
| Typical use | Launcher beams where fatigue life governs | Rails and beams where strength-to-weight governs |
Chemical composition (wt %)
Limits per GB/T 3190, which GJB 5077 tubes follow. Single values are maximums.
| Element | 2A12 | 7A09 |
|---|---|---|
| Si | 0.50 | 0.50 |
| Fe | 0.50 | 0.50 |
| Cu | 3.8 – 4.9 | 1.2 – 2.0 |
| Mn | 0.30 – 0.9 | 0.15 |
| Mg | 1.2 – 1.8 | 2.0 – 3.0 |
| Cr | — | 0.16 – 0.30 |
| Ni | 0.10 | — |
| Zn | 0.30 | 5.1 – 6.1 |
| Ti | 0.15 | 0.10 |
| Fe + Ni | 0.50 | — |
| Others each / total | 0.05 / 0.10 | 0.05 / 0.10 |
| Al | Remainder | Remainder |
Mechanical properties of launcher tubes
The values below are indicative longitudinal minimums for these tubes in the wall thicknesses used for launcher beams. The governing figures are those in the specification and on the drawing, and every lot is tested and certified.
| Alloy and temper | Wall thickness | Tensile strength Rm | Yield strength Rp0.2 | Elongation |
|---|---|---|---|---|
| 2A12-T3511 | About 18 – 60 mm sections | ≥ 420 MPa | ≥ 305 MPa | ≥ 7 % |
| 7A09-T6511 | About 30 – 38 mm sections | ≥ 510 MPa | ≥ 400 MPa | ≥ 5 % |
For comparison, ASTM B221 gives 2024-T3511 extrusions of similar thickness a minimum of about 414 MPa tensile and 290 – 300 MPa yield, and 7075-T6511 about 530 MPa tensile. The stretched tempers (the "511" suffix) are straightened by controlled stretching after quenching, which both relieves residual stress and improves straightness, an important advantage for long, slender beams.
Shape tolerances and surface requirements
Typical acceptance requirements
- Twist
- Not more than 2 mm per metre and 3 mm over the full length, unless the drawing states otherwise
- Straightness (bow)
- Measured as the largest gap under a straight edge; limit per specification or drawing
- Cross-section
- Per drawing; rail lands and fitting faces normally marked as critical
- Outer surface
- Free of cracks, corrosion and deep scratches; light oxidation discolouration and smooth spots are acceptable
- Inner surface
- Free of fish-scale (peeling) defects
- Coarse grain ring
- Depth of the peripheral coarse-grain layer checked on etched cross-sections against the specified limit
- Certification
- EN 10204 3.1 certificate with chemistry, tensile results and lot traceability
The coarse grain ring deserves attention. High-strength extrusions can recrystallise at the surface during solution treatment, forming a band of large grains with lower fatigue and stress-corrosion performance. Because launcher beams are machined at fittings, the depth of that band must stay inside the machining allowance or below the specified maximum.
Machining, joining and finishing
Joining
Use riveting, bolting or bonding. Neither 2A12 nor 7A09 is suited to fusion welding; friction stir welding is possible but must be qualified for the programme.
Surface protection
Sulphuric or boric-sulphuric anodising, or conversion coating with primer, is standard. Seal fastener holes to prevent crevice corrosion.
Inspection
Ultrasonic inspection, penetrant checks on machined faces and conductivity checks (7A09) can be specified with the order.
Where these tubes are used
- Airborne missile launchers: launcher beams and rail carriers on fixed-wing and rotary-wing aircraft
- Ground and ship launchers: lightweight rail and support beams where the same high strength is needed
- Aerospace structures: stringers and beams in spacecraft and rocket structures
- Other defence equipment: highly loaded frames and rails in vehicles and weapon mounts
References and standards
- GJB 5077-2001 – Specification for aluminium alloy special-shaped tubes for airborne missile launchers
- GB/T 3190 – Wrought aluminium and aluminium alloys: chemical composition
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles and Tubes
- EN 755-2 – Aluminium extruded rod, tube and profiles: mechanical properties
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
Missile launcher aluminium (aluminum) tubes: frequently asked questions
What is the international equivalent of 2A12 and 7A09?
2A12 corresponds closely to 2024 (EN AW-2024). 7A09 is very close to 7075, with slightly different copper and chromium limits. Programmes outside China usually specify 2024-T3511 or 7075-T6511 extrusions.
Why are launcher tubes supplied in T3511 or T6511?
The "511" tempers are stretched after quenching, which relieves residual stresses and straightens the extrusion. Long beams then stay straight and free of twist when they are machined.
Can 2A12 or 7A09 launcher tubes be welded?
Fusion welding is not recommended for either alloy because of hot cracking and loss of strength. Launcher assemblies are riveted, bolted or bonded.
What tolerances apply to launcher tubes?
Twist is commonly limited to 2 mm per metre and 3 mm over the length, with straightness and section tolerances set by the specification and drawing. Mark rail lands and fitting faces as critical dimensions.
Can you supply tubes to a custom section?
Yes. Shaped tubes are extruded to your drawing. Send the section, alloy, temper, length and quantity so the die and extrusion route can be reviewed.
Need launcher tubes or high-strength shaped extrusions?
Send the section drawing, alloy, temper and quantity. Our team will reply with a section review and quotation.
