T76 / T7651 (moderately overaged)
Aged past peak to gain good exfoliation-corrosion resistance and moderate stress-corrosion resistance, with a strength penalty of only a few per cent.
Aerospace · stretched 7xxx extrusions
7050 Aerospace Aluminium Extrusions & Profiles
7050 extrusions are used for stringers, spar caps, floor beams, seat tracks and frame members where an airframe needs high strength, good toughness and resistance to stress corrosion in one long, stiff section. They are supplied stretched and overaged in T76511, T74511 or T73511 to AMS 4340, AMS 4342 and AMS 4341. Metline supplies 7050 profiles, angles, tees, channels and extruded bar with full certification to aerospace buyers worldwide.
- Alloy
- 7050 (Al-Zn-Cu-Mg-Zr)
- Tempers
- T73511, T74511, T76511
- Shapes
- Angles, tees, Z, J, hat, I, bar
- Standards
- AMS 4340 · 4341 · 4342 · ASTM B221
The role of 7050 extrusions in an airframe
Long structural members in wings and fuselages, such as stringers, spar caps, frame chords, floor beams and seat tracks, are most efficiently made as extrusions: the cross-section is formed in one pass, and only local machining is needed. These members carry high axial loads and fatigue cycles for decades, so the alloy must be strong, tough and corrosion resistant along its whole length.
7050 meets these needs because its zirconium-controlled grain structure keeps strength through thick flanges and makes it far less quench sensitive than 7075. In the stretched and overaged T7xxx11 tempers it resists stress-corrosion cracking and exfoliation, which is critical for floor beams and seat tracks exposed to spills and condensation.
Compared with 7075-T6511 extrusions, 7050-T76511 gives similar or higher strength in thicker sections with much better exfoliation resistance, and 7050-T74511 gives strength well above 7075-T73511 with comparable stress-corrosion performance. That is why 7050 has displaced 7075 for many extruded parts on current aircraft.
7050 chemical composition (wt %)
Registered Aluminum Association limits, used by AMS 4340, 4341, 4342, ASTM B221 and EN 573-3. The "others" total is 0.15 % maximum, not 0.20 % as sometimes printed.
| Element | Minimum | Maximum | Role in the alloy |
|---|---|---|---|
| Silicon (Si) | — | 0.12 | Held very low for fracture toughness |
| Iron (Fe) | — | 0.15 | Held very low; fewer coarse intermetallics |
| Copper (Cu) | 2.0 | 2.6 | Raises strength and stress-corrosion resistance in T7 tempers |
| Manganese (Mn) | — | 0.10 | Residual |
| Magnesium (Mg) | 1.9 | 2.6 | Forms MgZn2 with zinc |
| Chromium (Cr) | — | 0.04 | Deliberately low; zirconium replaces it |
| Zinc (Zn) | 5.7 | 6.7 | Main strengthening element |
| Titanium (Ti) | — | 0.06 | Grain refiner |
| Zirconium (Zr) | 0.08 | 0.15 | Controls grain structure and lowers quench sensitivity |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder | About 87.3 – 90.3 % |
7050 extrusion properties by temper
Approximate typical values for extruded sections of moderate thickness are shown. AMS specifications set the binding minimums by thickness band, and some aircraft specifications add extra requirements for short-transverse properties and fracture toughness.
| Temper (specification) | Tensile strength (typical) | Yield strength (typical) | Elongation | Typical use |
|---|---|---|---|---|
| T76511 (AMS 4340) | About 550 MPa / 80 ksi | About 490 MPa / 71 ksi | About 9 – 11 % | Stringers, spar caps, frame chords |
| T74511 (AMS 4342) | About 515 MPa / 75 ksi | About 455 MPa / 66 ksi | About 10 – 12 % | Floor beams, seat tracks, fittings |
| T73511 (AMS 4341) | About 495 MPa / 72 ksi | About 435 MPa / 63 ksi | About 10 – 12 % | Parts with sustained transverse stress |
Physical properties
- Density
- 2.83 g/cm³ (0.102 lb/in³)
- Modulus of elasticity (tension)
- About 71.7 GPa (10,400 ksi)
- Shear modulus
- About 26.9 GPa
- Thermal conductivity
- About 155 – 160 W/m·K (T74 tempers)
- Electrical conductivity
- About 39 – 44 % IACS (T74 / T76), used as a check on the overaged temper
- Coefficient of thermal expansion
- About 23.5 µm/m·°C (20 – 100 °C)
- Melting range
- About 490 – 630 °C
Understanding the 7050 extrusion tempers
In a temper such as T76511, "T76" is the ageing condition, "5" means stress relieved by stretching, the next "1" means a controlled permanent set of about 1 – 3 %, and the final "1" means the product was straightened after stretching. T76510 and T74510 are the same without straightening.
T74 / T7451 (overaged)
A balance between strength and stress-corrosion resistance. The usual choice for thick 7050 plate, bar and forgings in wing and fuselage structure.
T73 / T7351 (fully overaged)
The highest resistance to stress-corrosion cracking of the 7xxx tempers, at roughly 10 – 15 % lower strength than T6. Chosen for short-transverse loaded fittings and parts in wet areas.
O (annealed) and F (as extruded) conditions are used only for material that will be heat-treated later. 7050 extrusions are not supplied in T1 or T3 tempers for aerospace use.
7050 extrusion shapes and sizes
| Shape | Typical size range | Notes |
|---|---|---|
| Angles (equal and unequal) | About 25 × 25 mm to 150 × 150 mm, walls 3 – 15 mm | Most common stringer and frame shape |
| Tees and bulb tees | Flange widths about 25 – 150 mm | Floor beams, stiffeners |
| Z, J and hat sections | To aircraft-manufacturer drawings | Stringers and frame chords |
| I sections and seat-track profiles | To drawing | Floor structure |
| Rectangular and square bar | To about 300 mm wide, thickness to 127 mm | Machining stock |
| Round bar and rod | About 10 – 127 mm diameter | Fittings, fasteners |
AMS 4340 covers bars, rods, wire, profiles and tubing up to 5 in (127 mm) in nominal diameter or least thickness. Most aerospace 7050 sections are produced against a specific die drawing, so please send the section drawing or the manufacturer part number with your enquiry.
Tolerances and inspection
Typical requirements
- Dimensional tolerances
- ANSI H35.2 standard tolerances or tighter limits on the section drawing
- Straightness and twist
- Controlled by stretching and straightening; checked along the full length
- Mechanical tests
- Tensile tests per lot at the locations and directions the specification sets
- Conductivity
- Eddy-current check confirming the overaged temper
- Ultrasonic
- For thicker sections and bar, to AMS-STD-2154 or ASTM B594
- Certification
- EN 10204 3.1 certificate, traceable to cast, extrusion and heat-treatment lot
Machining, joining and finishing
Machining
Machines well, with short chips. Stretched tempers stay straight when flanges are milled or pockets cut. Use sharp carbide and flood coolant.
Joining
Not weldable by MIG or TIG; earlier claims of good weldability for 7050 are wrong. Join with rivets, bolts or adhesive bonding.
Forming
Limited in the overaged tempers. Stringers needing contour are stretch-formed or formed before final ageing under controlled processes.
Corrosion protection
Anodise or apply conversion coating and primer; seal faying surfaces and fasteners in wet areas such as galleys and lavatories.
Where 7050 extrusions are used
- Wing: stringers, spar caps and rib chords
- Fuselage: stringers, frame chords and longerons
- Floor structure: floor beams and seat tracks, often T74511 or T73511 for corrosion resistance
- Cargo systems: cargo-floor rails and roller-track supports
- Helicopters and business jets: frames, beams and stiffeners
- Defence and space: missile body members and launch-vehicle stiffeners
7050 extrusions compared with 7075, 7150 and 2024
| Property | 7050-T76511 | 7075-T6511 | 7150-T77511 | 2024-T3511 |
|---|---|---|---|---|
| Typical tensile strength | About 550 MPa | About 570 MPa | About 610 MPa | About 485 MPa |
| Exfoliation resistance | Good | Poor | Good | Fair |
| Fracture toughness | Good | Moderate | Good | Good |
| Best suited to | General high-strength members | Thin, non-critical sections | Upper wing stringers | Tension members, lower wing |
How to order 7050 extrusions
- SpecifyAlloy and temper, section drawing or part number, lengths, quantity and the governing specification with its revision (AMS 4340, AMS 4341, AMS 4342 or ASTM B221).
- ConfirmWe confirm the specification can be met, the tolerance class, any extra tests (ultrasonic class, conductivity, fracture toughness) and the delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions, straightness or flatness 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, tensile results and conductivity where specified, traceable to the cast and lot number.
- Pack and shipExport packing in sealed, moisture-protected wooden cases or on pallets, with interleaving where surfaces are critical, shipped by sea or air to your port or door.
References and standards
- SAE AMS 4340 – Aluminum Alloy Extrusions, 7050-T76511
- SAE AMS 4342 – Aluminum Alloy Extrusions, 7050-T74511
- SAE AMS 4341 – Aluminum Alloy Extrusions, 7050-T73511
- ASTM B221 – Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- ANSI H35.2 – Dimensional Tolerances for Aluminum Mill Products
7050 aerospace aluminium (aluminum) extrusions: FAQ
Which temper should I order for 7050 extrusions?
Use the temper on the drawing. T76511 gives the highest strength, T74511 balances strength with stress-corrosion resistance, and T73511 gives the most stress-corrosion resistance.
Can 7050 extrusions be welded?
No, not by conventional arc welding. The alloy cracks and loses strength in the weld zone. Use rivets, bolts or bonding.
What is the maximum size of a 7050 extrusion?
AMS 4340 covers sections up to 5 in (127 mm) in least thickness or diameter. The overall size of a profile is limited by the die and press used.
Why is 7050 preferred to 7075 for seat tracks and floor beams?
In T74511 or T73511, 7050 resists stress corrosion and exfoliation much better than 7075-T6511 while keeping high strength, which suits areas exposed to moisture and spills.
Do you supply standard angles as well as custom profiles?
Yes. Common angles, tees and bars can be supplied, and custom aerospace sections are produced to drawing.
Need 7050 extrusions?
Send the section, temper, specification and quantity. We will reply with feasibility, certification and a delivered price.
