7049-T73511 (AMS 4157)
Fully overaged. Lowest strength of the two but the best resistance to stress-corrosion cracking in the short-transverse direction. Specified for fittings and gear parts loaded across the grain or exposed to moisture.
Aerospace · high-zinc 7xxx extrusions
7049 Aerospace Aluminium Extrusions (T73511 / T76511)
7049 is a high-zinc 7xxx alloy that keeps high strength in thick extruded sections while resisting stress-corrosion cracking when overaged. Its extrusions are ordered in T73511 to AMS 4157 or T76511 to AMS 4159 for landing-gear parts, fittings, stiffeners and other highly loaded airframe members. Metline supplies 7049 profiles, bars and machining stock with full certification to aerospace buyers worldwide.
- Alloy
- 7049 (Al-Zn-Mg-Cu-Cr)
- Tempers
- T73511, T76511
- Forms
- Profiles, bar, rod, tube
- Standards
- AMS 4157 · AMS 4159 · ASTM B221
What 7049 extrusions are used for
7049 carries about 7.7 % zinc, 2.4 % magnesium, 1.6 % copper and 0.16 % chromium. That is more zinc than 7075, which lets thick sections reach higher strength after quenching, while the copper and chromium help it tolerate the overageing treatments that protect against stress corrosion.
The alloy was developed for forgings and extrusions in landing gear and other heavily loaded, thick-section airframe parts, where 7075-T6 could crack in service if loaded across the grain. In the overaged T73 and T76 tempers 7049 keeps strength close to 7075-T6 while giving far better resistance to stress-corrosion cracking and exfoliation.
Today 7049 extrusions appear mainly on legacy and military platforms and in repair and spares programmes, where the drawing calls the alloy by name. For new designs, engineers often compare it with 7050 and 7150, which offer similar strength with better toughness. Buyers therefore usually order 7049 profiles in modest quantities against an existing part number and specification.
7049 chemical composition (wt %)
Limits follow the registered Aluminum Association values used by AMS 4157, AMS 4159 and ASTM B221. A closely related European variant, 7049A (EN AW-AlZn8MgCu), has slightly wider limits; confirm which one your drawing names.
| Element | Minimum | Maximum | Role in the alloy |
|---|---|---|---|
| Silicon (Si) | — | 0.25 | Impurity; kept low to protect toughness |
| Iron (Fe) | — | 0.35 | Impurity; forms coarse particles that start fatigue cracks |
| Copper (Cu) | 1.2 | 1.9 | Adds strength and improves stress-corrosion resistance in overaged tempers |
| Manganese (Mn) | — | 0.20 | Residual |
| Magnesium (Mg) | 2.0 | 2.9 | Combines with zinc to form the MgZn2 strengthening phase |
| Chromium (Cr) | 0.10 | 0.22 | Grain-structure control; resists recrystallisation |
| Zinc (Zn) | 7.2 | 8.2 | Main strengthening element |
| Titanium (Ti) | — | 0.10 | Grain refiner |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder | About 85.6 – 89.5 % |
Some published tables show copper at 0.06 – 0.16 % for 7049. That is not correct; the registered copper range is 1.2 – 1.9 %.
7049 extrusion properties by temper
The values below are approximate typical properties for extruded sections of moderate thickness. The binding numbers are the minimums in AMS 4157 or AMS 4159 for your thickness band and test direction, which appear on the mill certificate.
| Temper | Tensile strength (typical) | Yield strength (typical) | Elongation | Main reason to choose it |
|---|---|---|---|---|
| T76511 | About 540 – 570 MPa | About 480 – 510 MPa | About 8 – 10 % | Higher strength with good exfoliation resistance |
| T73511 | About 510 – 540 MPa | About 440 – 470 MPa | About 9 – 11 % | Maximum stress-corrosion resistance |
Physical properties
- Density
- About 2.84 g/cm³ (0.103 lb/in³)
- Modulus of elasticity
- About 72 GPa
- Thermal conductivity
- About 155 W/m·K (T73)
- Electrical conductivity
- About 40 % IACS (T73), used as a temper check
- Melting range
- About 475 – 625 °C
T73511 versus T76511
Both tempers are solution heat-treated, stretched about 1 – 3 % to relieve quench stresses (the "51"), straightened (the final "1") and then aged beyond peak strength. They differ in how far the ageing goes.
7049-T76511 (AMS 4159)
Moderately overaged. A few per cent stronger than T73511 with good exfoliation resistance. Used for stiffeners and members loaded mainly along the extrusion direction.
Why not T6?
Peak-aged 7049 has very high strength but poor stress-corrosion resistance in thick sections, so aerospace specifications concentrate on the overaged tempers.
7049 extrusion sizes and shapes
Supply range (by enquiry)
- Shapes
- Solid open profiles (angles, tees, channels, I and Z sections), bar, rod and machining stock; hollow sections by enquiry
- Thickness
- AMS 4159 covers products up to 5 in (127 mm) nominal diameter or least thickness
- Length
- Cut lengths or full extruded lengths to suit the part
- Condition
- Stretched and straightened, overaged to T73511 or T76511
- Testing
- Tensile, conductivity and ultrasonic inspection to the order specification
High-zinc 7xxx alloys extrude slowly and within tight temperature windows, so 7049 sections are usually made to order against a specific die.
Machining, joining and finishing
Machining
Machines well in the overaged tempers, with short chips and a good finish. Use sharp carbide tools and flood coolant; stretched tempers stay stable as material is removed.
Joining
Not suitable for fusion welding: like 7075, 7049 is prone to hot cracking and loses strength in the weld zone. Join by fasteners, rivets or adhesive bonding.
Surface protection
Anodise (chromic, boric-sulphuric or sulphuric) or apply a conversion coating and primer. Seal fastener holes in wet areas.
Heat exposure
Avoid prolonged exposure above about 120 °C, which over-ages the alloy further and lowers strength.
Where 7049 extrusions are used
- Landing gear: extruded stock for links, braces and fittings machined from thick sections
- Airframe structure: stiffeners, longerons and frame members on platforms that specify 7049
- Fittings: heavily loaded brackets and lugs where short-transverse stress-corrosion resistance matters
- Missiles and defence: structural members for airframes and launchers
- Maintenance and spares: replacement parts made to the original material specification
7049 compared with 7075, 7050 and 7149
| Property | 7049-T73511 | 7075-T73511 | 7050-T74511 | 7149-T73511 |
|---|---|---|---|---|
| Zinc content | 7.2 – 8.2 % | 5.1 – 6.1 % | 5.7 – 6.7 % | 7.2 – 8.2 % |
| Grain control element | Chromium | Chromium | Zirconium | Chromium |
| Strength in thick sections | High | Medium | High | High |
| Stress-corrosion resistance | Very good | Very good | Good–very good | Very good |
| Fracture toughness | Moderate | Moderate | Good | Better than 7049 (lower Fe, Si) |
7149 is essentially a higher-purity 7049 with tighter iron and silicon limits for better toughness. If your design allows a substitute, 7050-T74511 is the most widely available alternative.
How to order 7049 extrusions
- SpecifyAlloy and temper, profile drawing or section number, length, quantity and the governing specification with its revision (AMS 4157, AMS 4159 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 4157 – Aluminum Alloy Extrusions, 7049-T73511
- SAE AMS 4159 – Aluminum Alloy Extrusions, 7049-T76511
- 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)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
7049 aerospace aluminium (aluminum) extrusions: FAQ
What is the difference between 7049-T73511 and 7049-T76511?
Both are stretched, straightened and overaged. T73511 is aged further, giving the best stress-corrosion resistance at slightly lower strength; T76511 is a little stronger with good exfoliation resistance. Use the temper on your drawing.
Can 7049 extrusions be welded?
Not by conventional fusion welding. The alloy is crack-sensitive and the weld zone loses much of its strength, so parts are joined mechanically or bonded.
Is 7049 the same as 7049A?
They are close but not identical. 7049A is the European registration with slightly different limits. Where an aerospace specification names 7049, supply must meet the 7049 limits.
What can replace 7049 in a new design?
7050-T74511 and 7149-T73511 are the usual alternatives; both give similar strength and stress-corrosion resistance. Any substitution on an existing part needs the design authority to approve it.
Which specification covers 7049 extrusions?
AMS 4157 covers T73511 and AMS 4159 covers T76511. ASTM B221 covers general extruded products.
Need 7049 extrusions?
Send the profile, temper, specification and quantity. Our team will confirm feasibility, certification and a delivered price.
