Solution treatment
The section is heated to dissolve zinc, magnesium and copper, then quenched rapidly in water.
Aerospace · SCC-resistant extrusions
7175-T73511 Aerospace Aluminium Extrusions
7175-T73511 extrusions combine the stress-corrosion resistance of the over-aged T73 condition with the better toughness of a high-purity 7075-type alloy. Metline supplies 7175 extruded bars, rods and profiles to SAE AMS 4344, in thicknesses from 6.35 to 50.8 mm, to aerospace manufacturers worldwide.
- Alloy
- 7175 (high-purity 7075)
- Temper
- T73511
- Thickness
- 6.35 – 50.8 mm
- Spec
- AMS 4344
What 7175-T73511 extrusions are
7175 is 7075 with iron and silicon held to low levels. In extrusions it is supplied in T73511: solution heat-treated, stretched to relieve quench stress, straightened, and over-aged to the T73 level that gives the highest resistance to stress-corrosion cracking among the common 7xxx tempers.
The purity gain matters most for fatigue and toughness. Iron- and silicon-rich particles are the usual starting points for fatigue cracks in 7075, and they lower the energy needed to grow a crack. With fewer of them, 7175 extrusions perform better in damage-tolerance tests and show higher elongation in the transverse direction.
Typical uses are machined fittings, frames, chords and brackets made from extruded bar or profiles where a 7075-T73511 part is not tough enough, or where the designer wants extra fatigue margin without moving to a different alloy family. The AMS 4344 specification covers extruded bars, rods and profiles from 0.250 to 2.000 in (6.35 – 50.8 mm) in nominal thickness.
7175 chemical composition (wt %)
Registered limits for 7175 (UNS A97175). AMS 4344 gives the nominal chemistry as 5.6 Zn - 2.5 Mg - 1.6 Cu - 0.23 Cr.
| Element | Minimum | Maximum | Comment |
|---|---|---|---|
| Silicon (Si) | — | 0.15 | Lower than 7075 (0.40) for toughness |
| Iron (Fe) | — | 0.20 | Lower than 7075 (0.50); fewer fatigue-crack origins |
| Copper (Cu) | 1.2 | 2.0 | Strength and SCC resistance |
| Manganese (Mn) | — | 0.10 | Minor |
| Magnesium (Mg) | 2.1 | 2.9 | Forms MgZn2 with zinc |
| Chromium (Cr) | 0.18 | 0.28 | Grain control |
| Zinc (Zn) | 5.1 | 6.1 | Main strengthening element |
| Titanium (Ti) | — | 0.10 | Grain refiner |
| Others, each / total | — | 0.05 / 0.15 | |
| Aluminium (Al) | Remainder |
Data sheets showing 7175 with silicon up to 0.80 %, zinc of 5.0 – 6.0 % or properties such as 90 – 120 MPa tensile strength are wrong; those values describe a 6xxx alloy in the annealed condition.
Mechanical and physical properties
AMS 4344 sets minimum tensile properties by thickness band. Typical values for 7175-T73511 are similar to or slightly above 7075-T73511, with better elongation and toughness. Use the specification minimums or MMPDS values for design.
| Property (approx. typical) | 7175-T73511 | 7075-T73511 | 7075-T6511 |
|---|---|---|---|
| Tensile strength | About 505 – 525 MPa | About 505 MPa | About 570 MPa |
| Yield strength (0.2 %) | About 435 – 455 MPa | About 435 MPa | About 505 MPa |
| Elongation | About 12 % | About 12 % | About 11 % |
| Fracture toughness | Higher | Baseline | Lower |
| SCC resistance | Very high | Very high | Low |
Physical properties
- Density
- 2.80 g/cm³ (0.101 lb/in³)
- Modulus of elasticity
- About 72 GPa
- Electrical conductivity
- About 40 % IACS (T73511)
- Thermal conductivity
- About 155 W/m·K
- Coefficient of thermal expansion
- About 23.4 µm/m·°C
The T73511 temper
Stretching (51)
Stretched by a controlled permanent set, typically 1 – 3 %, to relieve quench stresses.
Straightening (1)
Minor straightening after stretching to meet straightness tolerances.
Over-ageing (T73)
Two-step artificial ageing beyond peak strength. Strength is about 10 – 15 % below T6 but SCC resistance is much higher.
Conductivity and hardness are measured on each lot. Because over-ageing raises electrical conductivity, a conductivity reading within the specified window confirms the part has been aged correctly.
7175 extrusion shapes and weights
| Product | Range | Notes |
|---|---|---|
| Rectangular bar | 6.35 – 50.8 mm thick | Width per extrusion capacity |
| Round bar and rod | Diameters up to the specification limit | Machining stock |
| Angles, tees, channels, Z and J sections | Per drawing | Thickness 6.35 – 50.8 mm |
| Lengths | Mill lengths or cut to size |
Weight of 7175 rectangular bar per metre (density 2.80 g/cm³):
| Section (mm) | kg per metre | kg per 4 m bar |
|---|---|---|
| 10 × 50 | 1.40 | 5.6 |
| 12.7 × 76.2 | 2.71 | 10.8 |
| 16 × 80 | 3.58 | 14.3 |
| 20 × 100 | 5.60 | 22.4 |
| 25.4 × 101.6 | 7.23 | 28.9 |
| 30 × 120 | 10.08 | 40.3 |
| 38.1 × 152.4 | 16.26 | 65.0 |
| 50.8 × 203.2 | 28.90 | 115.6 |
Tolerances, testing and certification
Typical requirements
- Dimensional tolerances
- To ANSI H35.2 or the drawing
- Tensile
- Longitudinal tests per lot; transverse on wider sections
- SCC and exfoliation
- Lot acceptance per AMS 4344
- Conductivity and hardness
- On each lot to confirm T73
- Ultrasonic
- To AMS-STD-2154 when ordered
- Certification
- EN 10204 3.1 certificate with chemistry, properties and lot traceability
Machining and finishing
Machining
Excellent machinability, similar to 7075-T73. Low residual stress from stretching keeps parts flat.
Joining
Bolted or riveted. Interference-fit fasteners and bushings are acceptable in T73 tempers.
Protection
Anodise or conversion coat and prime; seal faying surfaces.
Heat
Avoid long exposure above about 120 °C.
Where 7175 extrusions are used
- Fittings: wing-to-fuselage, pylon and control-surface fittings machined from extruded bar
- Frames and chords: fuselage frame segments and wing-rib chords
- Landing-gear bay structure: beams and supports exposed to moisture and de-icing fluid
- Helicopters and defence: structural sections where SCC resistance is required
How to order 7175 extrusions
- SpecifyAlloy and temper, section size or drawing, length, quantity and the governing specification with its revision letter (AMS 4344). Add any customer or prime-contractor material specification that sits on top of the AMS.
- ConfirmWe confirm the specification can be met, the tolerance class, any extra tests (ultrasonic class, conductivity, fracture toughness, grain flow) and the delivery terms (EXW, FOB, CIF or DAP).
- InspectMaterial is checked for dimensions, surface condition and marking; 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 giving chemistry, mechanical results and heat-treatment lot, traceable to the cast number.
- Pack and shipExport packing in sealed, moisture-protected wooden cases or on pallets, shipped by sea or air to your port or door.
References and standards
- SAE AMS 4344 – Extrusions, 5.6Zn - 2.5Mg - 1.6Cu - 0.23Cr (7175-T73511)
- ANSI H35.2 – Dimensional Tolerances for Aluminum Mill Products
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits (Teal Sheets)
- MMPDS – Metallic Materials Properties Development and Standardization (successor to MIL-HDBK-5)
- ASM Handbook, Vol. 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials
7175 aerospace aluminium (aluminum) extrusions: FAQ
Which specification covers 7175-T73511 extrusions?
SAE AMS 4344, for extruded bars, rods and profiles 0.250 to 2.000 in (6.35 to 50.8 mm) in nominal thickness.
Is 7175-T73511 stronger than 7075-T73511?
Strength is similar or slightly higher. The main gains are toughness, fatigue life and transverse ductility, thanks to the lower iron and silicon content.
Why use T73511 instead of T6511?
T73511 is over-aged for very high resistance to stress-corrosion cracking. T6511 is stronger but much more susceptible to SCC in loaded parts.
Can 7175 extrusions be welded?
No. They are joined by bolting or riveting.
Can I replace 7075-T73511 with 7175-T73511?
Technically 7175 meets or exceeds 7075 properties in this temper, but any substitution on an aircraft part needs approval from the design authority.
Do you ship 7175 extrusions worldwide?
Yes, with EN 10204 3.1 certificates and export packing.
Need 7175-T73511 extrusions?
Send the section, length, quantity and specification. We will confirm availability and a delivered price.
